diff --git a/.editorconfig b/.editorconfig
index be3654ef..8412c119 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -8,4 +8,4 @@ trim_trailing_whitespace = true
[*.{js,py}]
charset = utf-8
indent_style = space
-indent_size = 4
+indent_size = 2
diff --git a/.prettierrc b/.prettierrc
new file mode 100644
index 00000000..a2a849e3
--- /dev/null
+++ b/.prettierrc
@@ -0,0 +1,8 @@
+{
+ "bracketSpacing": false,
+ "jsxBracketSameLine": true,
+ "printWidth": 80,
+ "proseWrap": "never",
+ "singleQuote": true,
+ "trailingComma": "all"
+}
diff --git a/algorithms/README.md b/contents/algorithms/README.md
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diff --git a/algorithms/array.md b/contents/algorithms/array.md
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diff --git a/algorithms/dynamic-programming.md b/contents/algorithms/dynamic-programming.md
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diff --git a/algorithms/geometry.md b/contents/algorithms/geometry.md
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diff --git a/algorithms/graph.md b/contents/algorithms/graph.md
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diff --git a/algorithms/hash-table.md b/contents/algorithms/hash-table.md
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diff --git a/algorithms/heap.md b/contents/algorithms/heap.md
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diff --git a/algorithms/interval.md b/contents/algorithms/interval.md
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diff --git a/algorithms/linked-list.md b/contents/algorithms/linked-list.md
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diff --git a/algorithms/math.md b/contents/algorithms/math.md
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diff --git a/algorithms/matrix.md b/contents/algorithms/matrix.md
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diff --git a/algorithms/oop.md b/contents/algorithms/oop.md
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diff --git a/algorithms/permutation.md b/contents/algorithms/permutation.md
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diff --git a/algorithms/queue.md b/contents/algorithms/queue.md
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diff --git a/algorithms/sorting-searching.md b/contents/algorithms/sorting-searching.md
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diff --git a/algorithms/stack.md b/contents/algorithms/stack.md
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diff --git a/algorithms/string.md b/contents/algorithms/string.md
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diff --git a/algorithms/topics.md b/contents/algorithms/topics.md
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diff --git a/algorithms/tree.md b/contents/algorithms/tree.md
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diff --git a/non-technical/behavioral.md b/contents/non-technical/behavioral.md
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diff --git a/non-technical/cover-letter.md b/contents/non-technical/cover-letter.md
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diff --git a/non-technical/interview-formats.md b/contents/non-technical/interview-formats.md
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diff --git a/non-technical/negotiation.md b/contents/non-technical/negotiation.md
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diff --git a/non-technical/psychological-tricks.md b/contents/non-technical/psychological-tricks.md
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diff --git a/non-technical/questions-to-ask.md b/contents/non-technical/questions-to-ask.md
similarity index 100%
rename from non-technical/questions-to-ask.md
rename to contents/non-technical/questions-to-ask.md
diff --git a/non-technical/resume.md b/contents/non-technical/resume.md
similarity index 100%
rename from non-technical/resume.md
rename to contents/non-technical/resume.md
diff --git a/non-technical/self-introduction.md b/contents/non-technical/self-introduction.md
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rename to contents/non-technical/self-introduction.md
diff --git a/preparing/README.md b/contents/preparing/README.md
similarity index 100%
rename from preparing/README.md
rename to contents/preparing/README.md
diff --git a/contents/preparing/cheatsheet.md b/contents/preparing/cheatsheet.md
new file mode 100644
index 00000000..51f38d51
--- /dev/null
+++ b/contents/preparing/cheatsheet.md
@@ -0,0 +1,105 @@
+---
+id: interview-cheatsheet
+title: Interview Cheatsheet
+---
+
+This is a straight-to-the-point, distilled list of technical interview Do's and Don'ts, mainly for algorithmic interviews. Some of these may apply to only phone screens or whiteboard interviews, but most will apply to both. I revise this list before each of my interviews to remind myself of them and eventually internalized all of them to the point I do not have to rely on it anymore.
+
+For a detailed walkthrough of interview preparation, refer to the ["Preparing for a Coding Interview"](./) section.
+
+**Legend:** ✅ = Do, ❌ = Don't, ⚠️ = Situational
+
+### 1. Before Interview
+
+| | Things |
+| --- | --- |
+| ✅ | Prepare pen, paper and earphones/headphones. |
+| ✅ | Find a quiet environment with good Internet connection. |
+| ✅ | Ensure webcam and audio are working. There were times I had to restart Chrome to get Hangouts to work again. |
+| ✅ | Request for the option to interview over Hangouts/Skype instead of a phone call; it is easier to send links or text across. |
+| ✅ | Decide on and be familiar with a programming language. |
+| ✅ | Familiarize yourself with the coding environment (CoderPad/CodePen). Set up the coding shortcuts, turn on autocompletion, tab spacing, etc. |
+| ✅ | Prepare answers to the [frequently-asked questions](../non-technical/behavioral.md) in an interview. |
+| ✅ | Prepare some [questions to ask](../non-technical/questions-to-ask.md) at the end of the interview. |
+| ✅ | Dress comfortably. Usually you do not need to wear smart clothes, casual should be fine. T-shirts and jeans are acceptable at most places. |
+| ✅ | Stay calm and composed. |
+| ⚠️ | Turn off the webcam if possible. Most remote interviews will not require video chat and leaving it on only serves as a distraction. |
+
+### 2. Introduction
+
+| | Things |
+| --- | --- |
+| ✅ | Introduce yourself in a few sentences under a minute or two. |
+| ✅ | Mention interesting points that are relevant to the role you are applying for. |
+| ✅ | Sound enthusiastic! Speak with a smile and you will naturally sound more engaging. |
+| ❌ | Spend too long introducing yourself. The more time you spend talking the less time you have to code. |
+
+### 3. Upon Getting the Question
+
+| | Things |
+| --- | --- |
+| ✅ | Repeat the question back at the interviewer. |
+| ✅ | Clarify any assumptions you made subconsciously. Many questions are under-specified on purpose. A tree-like diagram could very well be a graph that allows for cycles and a naive recursive solution would not work. |
+| ✅ | Clarify input format and range. Ask whether input can be assumed to be well-formed and non-null. |
+| ✅ | Work through a small example to ensure you understood the question. |
+| ✅ | Explain a high level approach even if it is a brute force one. |
+| ✅ | Improve upon the approach and optimize. Reduce duplicated work and cache repeated computations. |
+| ✅ | Think carefully, then state and explain the time and space complexity of your approaches. |
+| ✅ | If stuck, think about related problems you have seen before and how they were solved. Check out the [tips](../algorithms) in this section. |
+| ❌ | Ignore information given to you. Every piece is important. |
+| ❌ | Jump into coding straightaway. |
+| ❌ | Start coding without interviewer's green light. |
+| ❌ | Appear too unsure about your approach or analysis. |
+
+### 4. During Coding
+
+| | Things |
+| --- | --- |
+| ✅ | Explain what you are coding/typing to the interviewer, what you are trying to achieve. |
+| ✅ | Practice good coding style. Clear variable names, consistent operator spacing, proper indentation, etc. |
+| ✅ | Type/write at a reasonable speed. |
+| ✅ | As much as possible, write actual compilable code, not pseudocode. |
+| ✅ | Write in a modular fashion. Extract out chunks of repeated code into functions. |
+| ✅ | Ask for permission to use trivial functions without having to implement them; saves you some time. |
+| ✅ | Use the hints given by the interviewer. |
+| ✅ | Demonstrate mastery of your chosen programming language. |
+| ✅ | Demonstrate technical knowledge in data structures and algorithms. |
+| ✅ | If you are cutting corners in your code, state that out loud to your interviewer and say what you would do in a non-interview setting (no time constraints). E.g., I would write a regex to parse this string rather than using `split()` which may not cover all cases. |
+| ✅ | Practice whiteboard space-management skills. |
+| ⚠️ | Reasonable defensive coding. Check for nulls, empty collections, etc. Can omit if input validity has been clarified with the interviewer. |
+| ❌ | Remain quiet the whole time. |
+| ❌ | Spend too much time writing comments. |
+| ❌ | Use extremely verbose variable names. |
+| ❌ | Copy and paste code without checking. |
+| ❌ | Interrupt your interviewer when they are talking. Usually if they speak, they are trying to give you hints or steer you in the right direction. |
+| ❌ | Write too big (takes up too much space) or too small (illegible) if on a whiteboard. |
+
+### 5. After Coding
+
+| | Things |
+| --- | --- |
+| ✅ | Scan through your code for mistakes as if it was your first time seeing code written by someone else. |
+| ✅ | Check for off-by-one errors. |
+| ✅ | Come up with more test cases. Try extreme test cases. |
+| ✅ | Step through your code with those test cases. |
+| ✅ | Look out for places where you can refactor. |
+| ✅ | Reiterate the time and space complexity of your code. |
+| ✅ | Explain trade-offs and how the code/approach can be improved if given more time. |
+| ❌ | Immediately announce that you are done coding. Do the above first! |
+| ❌ | Argue with the interviewer. They may be wrong but that is very unlikely given that they are familiar with the question. |
+
+### 6. Wrap Up
+
+| | Things |
+| --- | --- |
+| ✅ | Ask questions. More importantly, ask good and engaging questions that are tailored to the company! Pick some questions from [this list](../non-technical/questions-to-ask.md). |
+| ✅ | Thank the interviewer. |
+| ⚠️ | Ask about your interview performance. It can get awkward. |
+| ❌ | End the interview without asking any questions. |
+
+### 7. Post Interview
+
+| | Things |
+| --- | --- |
+| ✅ | Record the interview questions and answers down as these can be useful for future reference. |
+| ⚠️ | Send a follow up email to your interviewer(s) thanking them for their time and the opportunity to interview with them. |
diff --git a/design/README.md b/experimental/design/README.md
similarity index 100%
rename from design/README.md
rename to experimental/design/README.md
diff --git a/design/collaborative-editor.md b/experimental/design/collaborative-editor.md
similarity index 100%
rename from design/collaborative-editor.md
rename to experimental/design/collaborative-editor.md
diff --git a/design/news-feed.md b/experimental/design/news-feed.md
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rename from design/news-feed.md
rename to experimental/design/news-feed.md
diff --git a/design/search-engine.md b/experimental/design/search-engine.md
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rename from design/search-engine.md
rename to experimental/design/search-engine.md
diff --git a/domain/async-loading/index.html b/experimental/domain/async-loading/index.html
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rename from domain/async-loading/index.html
rename to experimental/domain/async-loading/index.html
diff --git a/domain/databases.md b/experimental/domain/databases.md
similarity index 100%
rename from domain/databases.md
rename to experimental/domain/databases.md
diff --git a/domain/networking.md b/experimental/domain/networking.md
similarity index 100%
rename from domain/networking.md
rename to experimental/domain/networking.md
diff --git a/domain/pagination-sorting/data.js b/experimental/domain/pagination-sorting/data.js
similarity index 100%
rename from domain/pagination-sorting/data.js
rename to experimental/domain/pagination-sorting/data.js
diff --git a/domain/pagination-sorting/index.html b/experimental/domain/pagination-sorting/index.html
similarity index 100%
rename from domain/pagination-sorting/index.html
rename to experimental/domain/pagination-sorting/index.html
diff --git a/domain/security.md b/experimental/domain/security.md
similarity index 100%
rename from domain/security.md
rename to experimental/domain/security.md
diff --git a/domain/snake-game/snake-game.md b/experimental/domain/snake-game/snake-game.md
similarity index 100%
rename from domain/snake-game/snake-game.md
rename to experimental/domain/snake-game/snake-game.md
diff --git a/domain/software-engineering.md b/experimental/domain/software-engineering.md
similarity index 100%
rename from domain/software-engineering.md
rename to experimental/domain/software-engineering.md
diff --git a/domain/tic-tac-toe/index.html b/experimental/domain/tic-tac-toe/index.html
similarity index 100%
rename from domain/tic-tac-toe/index.html
rename to experimental/domain/tic-tac-toe/index.html
diff --git a/front-end/README.md b/experimental/front-end/README.md
similarity index 100%
rename from front-end/README.md
rename to experimental/front-end/README.md
diff --git a/interviewers/basics.md b/experimental/interviewers/basics.md
similarity index 100%
rename from interviewers/basics.md
rename to experimental/interviewers/basics.md
diff --git a/utilities/javascript/binToInt.js b/experimental/utilities/javascript/binToInt.js
similarity index 68%
rename from utilities/javascript/binToInt.js
rename to experimental/utilities/javascript/binToInt.js
index c34a278d..35a87127 100644
--- a/utilities/javascript/binToInt.js
+++ b/experimental/utilities/javascript/binToInt.js
@@ -1,10 +1,10 @@
// Does not handle negative binary numbers.
function binToInt(binary) {
- let res = 0;
- for (let i = 0; i < binary.length; i++) {
- res = res * 2 + (+binary[i]);
- }
- return res;
+ let res = 0;
+ for (let i = 0; i < binary.length; i++) {
+ res = res * 2 + +binary[i];
+ }
+ return res;
}
console.log(binToInt('0') === parseInt('0', 2) && parseInt('0', 2) === 0);
@@ -12,4 +12,7 @@ console.log(binToInt('1') === parseInt('1', 2) && parseInt('1', 2) === 1);
console.log(binToInt('10') === parseInt('10', 2) && parseInt('10', 2) === 2);
console.log(binToInt('11') === parseInt('11', 2) && parseInt('11', 2) === 3);
console.log(binToInt('101') === parseInt('101', 2) && parseInt('101', 2) === 5);
-console.log(binToInt('1100011') === parseInt('1100011', 2) && parseInt('1100011', 2) === 99);
+console.log(
+ binToInt('1100011') === parseInt('1100011', 2) &&
+ parseInt('1100011', 2) === 99,
+);
diff --git a/utilities/javascript/binarySearch.js b/experimental/utilities/javascript/binarySearch.js
similarity index 60%
rename from utilities/javascript/binarySearch.js
rename to experimental/utilities/javascript/binarySearch.js
index 9ce8b336..e36f54bd 100644
--- a/utilities/javascript/binarySearch.js
+++ b/experimental/utilities/javascript/binarySearch.js
@@ -1,18 +1,18 @@
function binarySearch(arr, target) {
- let left = 0;
- let right = arr.length - 1;
- while (left <= right) {
- const mid = left + Math.floor((right - left) / 2);
- if (arr[mid] === target) {
- return mid;
- }
- if (arr[mid] < target) {
- left = mid + 1;
- } else {
- right = mid - 1;
- }
+ let left = 0;
+ let right = arr.length - 1;
+ while (left <= right) {
+ const mid = left + Math.floor((right - left) / 2);
+ if (arr[mid] === target) {
+ return mid;
}
- return -1;
+ if (arr[mid] < target) {
+ left = mid + 1;
+ } else {
+ right = mid - 1;
+ }
+ }
+ return -1;
}
console.log(binarySearch([1, 2, 3, 10], 1) === 0);
diff --git a/experimental/utilities/javascript/deepEqual.js b/experimental/utilities/javascript/deepEqual.js
new file mode 100644
index 00000000..826fdb20
--- /dev/null
+++ b/experimental/utilities/javascript/deepEqual.js
@@ -0,0 +1,43 @@
+function deepEqual(val1, val2) {
+ if (typeof val1 !== typeof val2) {
+ return false;
+ }
+
+ // Array comparison.
+ if (Array.isArray(val1) && Array.isArray(val2)) {
+ if (val1.length !== val2.length) {
+ return false;
+ }
+ for (let i = 0; i < val1.length; i++) {
+ if (!deepEqual(val1[i], val2[i])) {
+ return false;
+ }
+ }
+ return true;
+ }
+
+ // Object comparison.
+ if (
+ typeof val1 === 'object' &&
+ typeof val2 === 'object' &&
+ val1 !== null &&
+ val2 !== null
+ ) {
+ const keys1 = Object.keys(val1),
+ keys2 = Object.keys(val2);
+ if (keys1.length !== keys2.length) {
+ return false;
+ }
+ for (let i = 0; i < keys1.length; i++) {
+ if (!deepEqual(val1[keys1[i]], val2[keys2[i]])) {
+ return false;
+ }
+ }
+ return true;
+ }
+
+ // Primitive comparison.
+ return val1 === val2;
+}
+
+module.exports = deepEqual;
diff --git a/experimental/utilities/javascript/graphTopoSort.js b/experimental/utilities/javascript/graphTopoSort.js
new file mode 100644
index 00000000..3bbd8232
--- /dev/null
+++ b/experimental/utilities/javascript/graphTopoSort.js
@@ -0,0 +1,35 @@
+function graphTopoSort(numberNodes, edges) {
+ const nodes = new Map();
+ const order = [];
+ const queue = [];
+ for (let i = 0; i < numberNodes; i++) {
+ nodes.set(i, {in: 0, out: new Set()});
+ }
+
+ edges.forEach(edge => {
+ const [node_id, pre_id] = edge;
+ nodes.get(node_id).in += 1;
+ nodes.get(pre_id).out.add(node_id);
+ });
+
+ for (let [node_id, value] of nodes.entries()) {
+ if (value.in === 0) {
+ queue.push(node_id);
+ }
+ }
+
+ while (queue.length) {
+ const node_id = queue.shift();
+ for (let outgoing_id of nodes.get(node_id).out) {
+ nodes.get(outgoing_id).in -= 1;
+ if (nodes.get(outgoing_id).in === 0) {
+ queue.push(outgoing_id);
+ }
+ }
+ order.push(node_id);
+ }
+
+ return order.length == numberNodes ? order : [];
+}
+
+console.log(graphTopoSort(3, [[0, 1], [0, 2]]));
diff --git a/experimental/utilities/javascript/intToBin.js b/experimental/utilities/javascript/intToBin.js
new file mode 100644
index 00000000..187cdf1a
--- /dev/null
+++ b/experimental/utilities/javascript/intToBin.js
@@ -0,0 +1,21 @@
+// Does not handle negative numbers.
+function intToBin(number) {
+ if (number === 0) {
+ return '0';
+ }
+ let res = '';
+ while (number > 0) {
+ res = String(number % 2) + res;
+ number = parseInt(number / 2, 10);
+ }
+ return res;
+}
+
+console.log(intToBin(0) === (0).toString(2) && (0).toString(2) === '0');
+console.log(intToBin(1) === (1).toString(2) && (1).toString(2) === '1');
+console.log(intToBin(2) === (2).toString(2) && (2).toString(2) === '10');
+console.log(intToBin(3) === (3).toString(2) && (3).toString(2) === '11');
+console.log(intToBin(5) === (5).toString(2) && (5).toString(2) === '101');
+console.log(
+ intToBin(99) === (99).toString(2) && (99).toString(2) === '1100011',
+);
diff --git a/utilities/javascript/intervalsIntersect.js b/experimental/utilities/javascript/intervalsIntersect.js
similarity index 95%
rename from utilities/javascript/intervalsIntersect.js
rename to experimental/utilities/javascript/intervalsIntersect.js
index 2c6d59a0..4d13dfa8 100644
--- a/utilities/javascript/intervalsIntersect.js
+++ b/experimental/utilities/javascript/intervalsIntersect.js
@@ -1,6 +1,6 @@
// Interval: [start, end].
function intervalsIntersect(a, b) {
- return a[0] < b[1] && b[0] < a[1];
+ return a[0] < b[1] && b[0] < a[1];
}
console.log(intervalsIntersect([1, 2], [3, 4]) === false);
diff --git a/utilities/javascript/intervalsMerge.js b/experimental/utilities/javascript/intervalsMerge.js
similarity index 92%
rename from utilities/javascript/intervalsMerge.js
rename to experimental/utilities/javascript/intervalsMerge.js
index 795ca37a..b574f19d 100644
--- a/utilities/javascript/intervalsMerge.js
+++ b/experimental/utilities/javascript/intervalsMerge.js
@@ -1,7 +1,7 @@
// Interval: [start, end].
// Merges two overlapping intervals into one.
function intervalsMerge(a, b) {
- return [Math.min(a[0], b[0]), Math.max(a[1], b[1])];
+ return [Math.min(a[0], b[0]), Math.max(a[1], b[1])];
}
const deepEqual = require('./deepEqual');
diff --git a/utilities/javascript/isSubsequence.js b/experimental/utilities/javascript/isSubsequence.js
similarity index 56%
rename from utilities/javascript/isSubsequence.js
rename to experimental/utilities/javascript/isSubsequence.js
index b529399c..532ae26e 100644
--- a/utilities/javascript/isSubsequence.js
+++ b/experimental/utilities/javascript/isSubsequence.js
@@ -1,14 +1,14 @@
function isSubsequence(s, t) {
- if (s.length > t.length) {
- return false;
+ if (s.length > t.length) {
+ return false;
+ }
+ let matchedLength = 0;
+ for (let i = 0; i < t.length; i++) {
+ if (matchedLength < s.length && s[matchedLength] === t[i]) {
+ matchedLength += 1;
}
- let matchedLength = 0;
- for (let i = 0; i < t.length; i++) {
- if (matchedLength < s.length && s[matchedLength] === t[i]) {
- matchedLength += 1;
- }
- }
- return matchedLength === s.length;
+ }
+ return matchedLength === s.length;
}
console.log(isSubsequence('abc', 'abcde') === true);
diff --git a/utilities/javascript/matrixClone.js b/experimental/utilities/javascript/matrixClone.js
similarity index 64%
rename from utilities/javascript/matrixClone.js
rename to experimental/utilities/javascript/matrixClone.js
index b3f3f996..2dc00dc2 100644
--- a/utilities/javascript/matrixClone.js
+++ b/experimental/utilities/javascript/matrixClone.js
@@ -1,7 +1,9 @@
function matrixClone(matrix, defaultValue) {
- return matrix.map(row => {
- return defaultValue === undefined ? row.slice(0) : Array(row.length).fill(defaultValue);
- });
+ return matrix.map(row => {
+ return defaultValue === undefined
+ ? row.slice(0)
+ : Array(row.length).fill(defaultValue);
+ });
}
const deepEqual = require('./deepEqual');
@@ -15,4 +17,6 @@ console.log(deepEqual(matrixClone([[1]]), [[1]]));
// Test clone with default value.
console.log(deepEqual(matrixClone([[1, 2], [1, 4]], 1), [[1, 1], [1, 1]]));
-console.log(deepEqual(matrixClone([[1, 2], [1, 4]], null), [[null, null], [null, null]]));
+console.log(
+ deepEqual(matrixClone([[1, 2], [1, 4]], null), [[null, null], [null, null]]),
+);
diff --git a/utilities/javascript/matrixTranspose.js b/experimental/utilities/javascript/matrixTranspose.js
similarity index 63%
rename from utilities/javascript/matrixTranspose.js
rename to experimental/utilities/javascript/matrixTranspose.js
index 0418a426..134dc918 100644
--- a/utilities/javascript/matrixTranspose.js
+++ b/experimental/utilities/javascript/matrixTranspose.js
@@ -1,5 +1,5 @@
function matrixTranspose(matrix) {
- return matrix[0].map((col, i) => matrix.map(row => row[i]));
+ return matrix[0].map((col, i) => matrix.map(row => row[i]));
}
const deepEqual = require('./deepEqual');
@@ -7,5 +7,6 @@ const deepEqual = require('./deepEqual');
console.log(deepEqual(matrixTranspose([[1]]), [[1]]));
console.log(deepEqual(matrixTranspose([[1, 2]]), [[1], [2]]));
console.log(deepEqual(matrixTranspose([[1, 2], [1, 4]]), [[1, 1], [2, 4]]));
-console.log(deepEqual(matrixTranspose([[1, 2, 3], [4, 5, 6]]), [[1, 4], [2, 5], [3, 6]]));
-
+console.log(
+ deepEqual(matrixTranspose([[1, 2, 3], [4, 5, 6]]), [[1, 4], [2, 5], [3, 6]]),
+);
diff --git a/experimental/utilities/javascript/matrixTraverse.js b/experimental/utilities/javascript/matrixTraverse.js
new file mode 100644
index 00000000..40619f78
--- /dev/null
+++ b/experimental/utilities/javascript/matrixTraverse.js
@@ -0,0 +1,30 @@
+function traverse(matrix) {
+ const DIRECTIONS = [[0, 1], [0, -1], [1, 0], [-1, 0]];
+ const rows = matrix.length;
+ const cols = matrix[0].length;
+ const visited = matrix.map(row => Array(row.length).fill(false));
+ function dfs(i, j) {
+ if (visited[i][j]) {
+ return;
+ }
+ visited[i][j] = true;
+ DIRECTIONS.forEach(dir => {
+ const row = i + dir[0],
+ col = j + dir[1];
+ // Boundary check.
+ if (row < 0 || row >= rows || col < 0 || col >= cols) {
+ return;
+ }
+ // Valid neighbor check.
+ if (matrix[row][col] !== 1) {
+ return;
+ }
+ dfs(row, col);
+ });
+ }
+ for (let i = 0; i < rows; i++) {
+ for (let j = 0; j < cols; j++) {
+ dfs(i, j);
+ }
+ }
+}
diff --git a/experimental/utilities/javascript/mergeSort.js b/experimental/utilities/javascript/mergeSort.js
new file mode 100644
index 00000000..49cf2469
--- /dev/null
+++ b/experimental/utilities/javascript/mergeSort.js
@@ -0,0 +1,62 @@
+function mergeSort(arr) {
+ if (arr.length < 2) {
+ // Arrays of length 0 or 1 are sorted by definition.
+ return arr;
+ }
+
+ const left = arr.slice(0, Math.floor(arr.length / 2));
+ const right = arr.slice(Math.floor(arr.length / 2), Math.floor(arr.length));
+
+ return merge(mergeSort(left), mergeSort(right));
+}
+
+function merge(arr1, arr2) {
+ const merged = [];
+ let i = 0,
+ j = 0;
+
+ while (i < arr1.length && j < arr2.length) {
+ if (arr1[i] <= arr2[j]) {
+ merged.push(arr1[i]);
+ i++;
+ } else if (arr2[j] < arr1[i]) {
+ merged.push(arr2[j]);
+ j++;
+ }
+ }
+
+ merged.push(...arr1.slice(i), ...arr2.slice(j));
+ return merged;
+}
+
+const deepEqual = require('./deepEqual');
+
+console.log(deepEqual(mergeSort([]), []));
+console.log(deepEqual(mergeSort([1]), [1]));
+console.log(deepEqual(mergeSort([2, 1]), [1, 2]));
+console.log(deepEqual(mergeSort([7, 2, 4, 3, 1, 2]), [1, 2, 2, 3, 4, 7]));
+console.log(deepEqual(mergeSort([1, 2, 3, 4, 5, 0]), [0, 1, 2, 3, 4, 5]));
+console.log(
+ deepEqual(mergeSort([10, 9, 8, 7, 6, 5, 4, 3, 2, 1]), [
+ 1,
+ 2,
+ 3,
+ 4,
+ 5,
+ 6,
+ 7,
+ 8,
+ 9,
+ 10,
+ ]),
+);
+console.log(
+ deepEqual(mergeSort([98322, 3242, 876, -234, 34, 12331]), [
+ -234,
+ 34,
+ 876,
+ 3242,
+ 12331,
+ 98322,
+ ]),
+);
diff --git a/experimental/utilities/javascript/treeEqual.js b/experimental/utilities/javascript/treeEqual.js
new file mode 100644
index 00000000..e5c23c0a
--- /dev/null
+++ b/experimental/utilities/javascript/treeEqual.js
@@ -0,0 +1,13 @@
+function treeEqual(node1, node2) {
+ if (!node1 && !node2) {
+ return true;
+ }
+ if (!node1 || !node2) {
+ return false;
+ }
+ return (
+ node1.val == node2.val &&
+ treeEqual(node1.left, node2.left) &&
+ treeEqual(node1.right, node2.right)
+ );
+}
diff --git a/experimental/utilities/javascript/treeMirror.js b/experimental/utilities/javascript/treeMirror.js
new file mode 100644
index 00000000..ad8be653
--- /dev/null
+++ b/experimental/utilities/javascript/treeMirror.js
@@ -0,0 +1,10 @@
+function treeMirror(node) {
+ if (!node) {
+ return;
+ }
+ let temp = node.left;
+ node.left = node.right;
+ node.right = temp;
+ treeMirror(node.left);
+ treeMirror(node.right);
+}
diff --git a/utilities/python/binary_search.py b/experimental/utilities/python/binary_search.py
similarity index 99%
rename from utilities/python/binary_search.py
rename to experimental/utilities/python/binary_search.py
index 4e664c72..b0f97c4a 100644
--- a/utilities/python/binary_search.py
+++ b/experimental/utilities/python/binary_search.py
@@ -66,4 +66,3 @@ print(bisect_right([1, 2, 3, 3, 10], 10) == 5)
print(bisect_right([1, 2, 3, 3, 10], 9) == 4)
print(bisect_right([1, 2, 3, 3, 10], 0) == 0) # Insert "0" at front
print(bisect_right([1, 2, 3, 3, 10], 11) == 5) # Insert "5" at back
-
diff --git a/utilities/python/char_prime_map.py b/experimental/utilities/python/char_prime_map.py
similarity index 100%
rename from utilities/python/char_prime_map.py
rename to experimental/utilities/python/char_prime_map.py
diff --git a/utilities/python/graph_dfs.py b/experimental/utilities/python/graph_dfs.py
similarity index 100%
rename from utilities/python/graph_dfs.py
rename to experimental/utilities/python/graph_dfs.py
diff --git a/utilities/python/graph_topo_sort.py b/experimental/utilities/python/graph_topo_sort.py
similarity index 100%
rename from utilities/python/graph_topo_sort.py
rename to experimental/utilities/python/graph_topo_sort.py
diff --git a/utilities/python/heap.py b/experimental/utilities/python/heap.py
similarity index 100%
rename from utilities/python/heap.py
rename to experimental/utilities/python/heap.py
diff --git a/utilities/python/is_subsequence.py b/experimental/utilities/python/is_subsequence.py
similarity index 100%
rename from utilities/python/is_subsequence.py
rename to experimental/utilities/python/is_subsequence.py
diff --git a/utilities/python/linked_list.py b/experimental/utilities/python/linked_list.py
similarity index 100%
rename from utilities/python/linked_list.py
rename to experimental/utilities/python/linked_list.py
diff --git a/utilities/python/quick_select.py b/experimental/utilities/python/quick_select.py
similarity index 100%
rename from utilities/python/quick_select.py
rename to experimental/utilities/python/quick_select.py
diff --git a/utilities/python/rabin_karp_hash.py b/experimental/utilities/python/rabin_karp_hash.py
similarity index 100%
rename from utilities/python/rabin_karp_hash.py
rename to experimental/utilities/python/rabin_karp_hash.py
diff --git a/utilities/python/tree_equal.py b/experimental/utilities/python/tree_equal.py
similarity index 100%
rename from utilities/python/tree_equal.py
rename to experimental/utilities/python/tree_equal.py
diff --git a/utilities/python/tree_mirror.py b/experimental/utilities/python/tree_mirror.py
similarity index 100%
rename from utilities/python/tree_mirror.py
rename to experimental/utilities/python/tree_mirror.py
diff --git a/utilities/python/tree_traversal.py b/experimental/utilities/python/tree_traversal.py
similarity index 100%
rename from utilities/python/tree_traversal.py
rename to experimental/utilities/python/tree_traversal.py
diff --git a/utilities/python/trie.py b/experimental/utilities/python/trie.py
similarity index 100%
rename from utilities/python/trie.py
rename to experimental/utilities/python/trie.py
diff --git a/utilities/python/union_find.py b/experimental/utilities/python/union_find.py
similarity index 100%
rename from utilities/python/union_find.py
rename to experimental/utilities/python/union_find.py
diff --git a/preparing/cheatsheet.md b/preparing/cheatsheet.md
deleted file mode 100644
index 96f4b210..00000000
--- a/preparing/cheatsheet.md
+++ /dev/null
@@ -1,105 +0,0 @@
----
-id: interview-cheatsheet
-title: Interview Cheatsheet
----
-
-This is a straight-to-the-point, distilled list of technical interview Do's and Don'ts, mainly for algorithmic interviews. Some of these may apply to only phone screens or whiteboard interviews, but most will apply to both. I revise this list before each of my interviews to remind myself of them and eventually internalized all of them to the point I do not have to rely on it anymore.
-
-For a detailed walkthrough of interview preparation, refer to the ["Preparing for a Coding Interview"](./) section.
-
-**Legend:** ✅ = Do, ❌ = Don't, ⚠️ = Situational
-
-### 1. Before Interview
-
-|| Things |
-|-|-|
-|✅|Prepare pen, paper and earphones/headphones.|
-|✅|Find a quiet environment with good Internet connection.|
-|✅|Ensure webcam and audio are working. There were times I had to restart Chrome to get Hangouts to work again.|
-|✅|Request for the option to interview over Hangouts/Skype instead of a phone call; it is easier to send links or text across.|
-|✅|Decide on and be familiar with a programming language.|
-|✅|Familiarize yourself with the coding environment (CoderPad/CodePen). Set up the coding shortcuts, turn on autocompletion, tab spacing, etc.|
-|✅|Prepare answers to the [frequently-asked questions](../non-technical/behavioral.md) in an interview.|
-|✅|Prepare some [questions to ask](../non-technical/questions-to-ask.md) at the end of the interview.|
-|✅|Dress comfortably. Usually you do not need to wear smart clothes, casual should be fine. T-shirts and jeans are acceptable at most places.|
-|✅|Stay calm and composed.|
-|⚠️|Turn off the webcam if possible. Most remote interviews will not require video chat and leaving it on only serves as a distraction.|
-
-### 2. Introduction
-
-|| Things |
-|-|-|
-|✅|Introduce yourself in a few sentences under a minute or two.|
-|✅|Mention interesting points that are relevant to the role you are applying for.|
-|✅|Sound enthusiastic! Speak with a smile and you will naturally sound more engaging.|
-|❌|Spend too long introducing yourself. The more time you spend talking the less time you have to code.|
-
-### 3. Upon Getting the Question
-
-|| Things |
-|-|-|
-|✅|Repeat the question back at the interviewer.|
-|✅|Clarify any assumptions you made subconsciously. Many questions are under-specified on purpose. A tree-like diagram could very well be a graph that allows for cycles and a naive recursive solution would not work.|
-|✅|Clarify input format and range. Ask whether input can be assumed to be well-formed and non-null.|
-|✅|Work through a small example to ensure you understood the question.|
-|✅|Explain a high level approach even if it is a brute force one.|
-|✅|Improve upon the approach and optimize. Reduce duplicated work and cache repeated computations.|
-|✅|Think carefully, then state and explain the time and space complexity of your approaches.|
-|✅|If stuck, think about related problems you have seen before and how they were solved. Check out the [tips](../algorithms) in this section.|
-|❌|Ignore information given to you. Every piece is important.|
-|❌|Jump into coding straightaway.|
-|❌|Start coding without interviewer's green light.|
-|❌|Appear too unsure about your approach or analysis.|
-
-### 4. During Coding
-
-|| Things |
-|-|-|
-|✅|Explain what you are coding/typing to the interviewer, what you are trying to achieve.|
-|✅|Practice good coding style. Clear variable names, consistent operator spacing, proper indentation, etc.|
-|✅|Type/write at a reasonable speed.|
-|✅|As much as possible, write actual compilable code, not pseudocode.|
-|✅|Write in a modular fashion. Extract out chunks of repeated code into functions.|
-|✅|Ask for permission to use trivial functions without having to implement them; saves you some time.|
-|✅|Use the hints given by the interviewer.|
-|✅|Demonstrate mastery of your chosen programming language.|
-|✅|Demonstrate technical knowledge in data structures and algorithms.|
-|✅|If you are cutting corners in your code, state that out loud to your interviewer and say what you would do in a non-interview setting (no time constraints). E.g., I would write a regex to parse this string rather than using `split()` which may not cover all cases.|
-|✅|Practice whiteboard space-management skills.|
-|⚠️|Reasonable defensive coding. Check for nulls, empty collections, etc. Can omit if input validity has been clarified with the interviewer.|
-|❌|Remain quiet the whole time.|
-|❌|Spend too much time writing comments.|
-|❌|Use extremely verbose variable names.|
-|❌|Copy and paste code without checking.|
-|❌|Interrupt your interviewer when they are talking. Usually if they speak, they are trying to give you hints or steer you in the right direction.|
-|❌|Write too big (takes up too much space) or too small (illegible) if on a whiteboard.|
-
-### 5. After Coding
-
-|| Things |
-|-|-|
-|✅|Scan through your code for mistakes as if it was your first time seeing code written by someone else.|
-|✅|Check for off-by-one errors.|
-|✅|Come up with more test cases. Try extreme test cases.|
-|✅|Step through your code with those test cases.|
-|✅|Look out for places where you can refactor.|
-|✅|Reiterate the time and space complexity of your code.|
-|✅|Explain trade-offs and how the code/approach can be improved if given more time.|
-|❌|Immediately announce that you are done coding. Do the above first!|
-|❌|Argue with the interviewer. They may be wrong but that is very unlikely given that they are familiar with the question.|
-
-### 6. Wrap Up
-
-|| Things |
-|-|-|
-|✅|Ask questions. More importantly, ask good and engaging questions that are tailored to the company! Pick some questions from [this list](../non-technical/questions-to-ask.md).|
-|✅|Thank the interviewer.|
-|⚠️|Ask about your interview performance. It can get awkward.|
-|❌|End the interview without asking any questions.|
-
-### 7. Post Interview
-
-|| Things |
-|-|-|
-|✅|Record the interview questions and answers down as these can be useful for future reference.|
-|⚠️|Send a follow up email to your interviewer(s) thanking them for their time and the opportunity to interview with them.|
diff --git a/utilities/javascript/deepEqual.js b/utilities/javascript/deepEqual.js
deleted file mode 100644
index d2c9f649..00000000
--- a/utilities/javascript/deepEqual.js
+++ /dev/null
@@ -1,37 +0,0 @@
-function deepEqual(val1, val2) {
- if (typeof val1 !== typeof val2) {
- return false;
- }
-
- // Array comparison.
- if (Array.isArray(val1) && Array.isArray(val2)) {
- if (val1.length !== val2.length) {
- return false;
- }
- for (let i = 0; i < val1.length; i++) {
- if (!deepEqual(val1[i], val2[i])) {
- return false;
- }
- }
- return true;
- }
-
- // Object comparison.
- if (typeof val1 === 'object' && typeof val2 === 'object' && val1 !== null && val2 !== null) {
- const keys1 = Object.keys(val1), keys2 = Object.keys(val2);
- if (keys1.length !== keys2.length) {
- return false;
- }
- for (let i = 0; i < keys1.length; i++) {
- if (!deepEqual(val1[keys1[i]], val2[keys2[i]])) {
- return false;
- }
- }
- return true;
- }
-
- // Primitive comparison.
- return val1 === val2;
-}
-
-module.exports = deepEqual;
diff --git a/utilities/javascript/graphTopoSort.js b/utilities/javascript/graphTopoSort.js
deleted file mode 100644
index 13468026..00000000
--- a/utilities/javascript/graphTopoSort.js
+++ /dev/null
@@ -1,35 +0,0 @@
-function graphTopoSort(numberNodes, edges) {
- const nodes = new Map();
- const order = [];
- const queue = [];
- for (let i = 0; i < numberNodes; i++) {
- nodes.set(i, { in: 0, out: new Set() });
- }
-
- edges.forEach(edge => {
- const [node_id, pre_id] = edge;
- nodes.get(node_id).in += 1;
- nodes.get(pre_id).out.add(node_id);
- });
-
- for (let [node_id, value] of nodes.entries()) {
- if (value.in === 0) {
- queue.push(node_id);
- }
- }
-
- while (queue.length) {
- const node_id = queue.shift();
- for (let outgoing_id of nodes.get(node_id).out) {
- nodes.get(outgoing_id).in -= 1;
- if (nodes.get(outgoing_id).in === 0) {
- queue.push(outgoing_id);
- }
- }
- order.push(node_id);
- }
-
- return order.length == numberNodes ? order : [];
-}
-
-console.log(graphTopoSort(3, [[0, 1], [0, 2]]));
diff --git a/utilities/javascript/intToBin.js b/utilities/javascript/intToBin.js
deleted file mode 100644
index 6d33e7e5..00000000
--- a/utilities/javascript/intToBin.js
+++ /dev/null
@@ -1,19 +0,0 @@
-// Does not handle negative numbers.
-function intToBin(number) {
- if (number === 0) {
- return '0';
- }
- let res = '';
- while (number > 0) {
- res = String(number % 2) + res;
- number = parseInt(number / 2, 10);
- }
- return res;
-}
-
-console.log(intToBin(0) === 0..toString(2) && 0..toString(2) === '0');
-console.log(intToBin(1) === 1..toString(2) && 1..toString(2) === '1');
-console.log(intToBin(2) === 2..toString(2) && 2..toString(2) === '10');
-console.log(intToBin(3) === 3..toString(2) && 3..toString(2) === '11');
-console.log(intToBin(5) === 5..toString(2) && 5..toString(2) === '101');
-console.log(intToBin(99) === 99..toString(2) && 99..toString(2) === '1100011');
diff --git a/utilities/javascript/matrixTraverse.js b/utilities/javascript/matrixTraverse.js
deleted file mode 100644
index 331a24e4..00000000
--- a/utilities/javascript/matrixTraverse.js
+++ /dev/null
@@ -1,28 +0,0 @@
-function traverse(matrix) {
- const DIRECTIONS = [[0, 1], [0, -1], [1, 0], [-1, 0]];
- const rows = matrix.length, cols = matrix[0].length;
- const visited = matrix.map(row => Array(row.length).fill(false));
- function dfs(i, j) {
- if (visited[i][j]) {
- return;
- }
- visited[i][j] = true;
- DIRECTIONS.forEach(dir => {
- const row = i + dir[0], col = j + dir[1];
- // Boundary check.
- if (row < 0 || row >= rows || col < 0 || col >= cols) {
- return;
- }
- // Valid neighbor check.
- if (matrix[row][col] !== 1) {
- return;
- }
- dfs(row, col);
- });
- }
- for (let i = 0; i < rows; i++) {
- for (let j = 0; j < cols; j++) {
- dfs(i, j);
- }
- }
-}
diff --git a/utilities/javascript/mergeSort.js b/utilities/javascript/mergeSort.js
deleted file mode 100644
index d66537fd..00000000
--- a/utilities/javascript/mergeSort.js
+++ /dev/null
@@ -1,60 +0,0 @@
-function mergeSort(arr) {
- if (arr.length < 2) {
- // Arrays of length 0 or 1 are sorted by definition.
- return arr;
- }
-
- const left = arr.slice(0, Math.floor(arr.length / 2));
- const right = arr.slice(Math.floor(arr.length / 2), Math.floor(arr.length));
-
- return merge(mergeSort(left), mergeSort(right));
-}
-
-function merge(arr1, arr2) {
- const merged = [];
- let i = 0, j = 0;
-
- while (i < arr1.length && j < arr2.length) {
- if (arr1[i] <= arr2[j]) {
- merged.push(arr1[i]);
- i++;
- } else if (arr2[j] < arr1[i]) {
- merged.push(arr2[j]);
- j++;
- }
- }
-
- merged.push(...arr1.slice(i), ...arr2.slice(j));
- return merged;
-}
-
-const deepEqual = require('./deepEqual');
-
-console.log(deepEqual(
- mergeSort([]),
- [],
-));
-console.log(deepEqual(
- mergeSort([1]),
- [1],
-));
-console.log(deepEqual(
- mergeSort([2, 1]),
- [1, 2],
-));
-console.log(deepEqual(
- mergeSort([7, 2, 4, 3, 1, 2]),
- [1, 2, 2, 3, 4, 7],
-));
-console.log(deepEqual(
- mergeSort([1, 2, 3, 4, 5, 0]),
- [0, 1, 2, 3, 4, 5],
-));
-console.log(deepEqual(
- mergeSort([10, 9, 8, 7, 6, 5, 4, 3, 2, 1]),
- [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
-));
-console.log(deepEqual(
- mergeSort([98322, 3242, 876, -234, 34, 12331]),
- [-234, 34, 876, 3242, 12331, 98322],
-));
diff --git a/utilities/javascript/treeEqual.js b/utilities/javascript/treeEqual.js
deleted file mode 100644
index 10774619..00000000
--- a/utilities/javascript/treeEqual.js
+++ /dev/null
@@ -1,11 +0,0 @@
-function treeEqual(node1, node2) {
- if (!node1 && !node2) {
- return true;
- }
- if (!node1 || !node2) {
- return false;
- }
- return node1.val == node2.val &&
- treeEqual(node1.left, node2.left) &&
- treeEqual(node1.right, node2.right);
-}
diff --git a/utilities/javascript/treeMirror.js b/utilities/javascript/treeMirror.js
deleted file mode 100644
index 63d37155..00000000
--- a/utilities/javascript/treeMirror.js
+++ /dev/null
@@ -1,10 +0,0 @@
-function treeMirror(node) {
- if (!node) {
- return;
- }
- let temp = node.left;
- node.left = node.right;
- node.right = temp;
- treeMirror(node.left);
- treeMirror(node.right);
-}