Add a ton of JS algo snippets (#56)

utilities/javascript/binToInt.js

@@ -0,0 +1,15 @@
+// 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;
+}
+
+console.log(binToInt('0') === parseInt('0', 2) && parseInt('0', 2) === 0);
+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);

utilities/javascript/binarySearch.js

@@ -15,12 +15,12 @@ function binarySearch(arr, target) {
     return -1;
 }
 
-console.log(binarySearch([1, 2, 3, 10], 1) === 0)
+console.log(binarySearch([1, 2, 3, 10], 1) === 0);
-console.log(binarySearch([1, 2, 3, 10], 2) === 1)
+console.log(binarySearch([1, 2, 3, 10], 2) === 1);
-console.log(binarySearch([1, 2, 3, 10], 3) === 2)
+console.log(binarySearch([1, 2, 3, 10], 3) === 2);
-console.log(binarySearch([1, 2, 3, 10], 10) === 3)
+console.log(binarySearch([1, 2, 3, 10], 10) === 3);
-console.log(binarySearch([1, 2, 3, 10], 9) === -1)
+console.log(binarySearch([1, 2, 3, 10], 9) === -1);
-console.log(binarySearch([1, 2, 3, 10], 4) === -1)
+console.log(binarySearch([1, 2, 3, 10], 4) === -1);
-console.log(binarySearch([1, 2, 3, 10], 0) === -1)
+console.log(binarySearch([1, 2, 3, 10], 0) === -1);
-console.log(binarySearch([1, 2, 3, 10], 11) === -1)
+console.log(binarySearch([1, 2, 3, 10], 11) === -1);
-console.log(binarySearch([5, 7, 8, 10], 3) === -1)
+console.log(binarySearch([5, 7, 8, 10], 3) === -1);

utilities/javascript/deepEqual.js

@@ -17,9 +17,8 @@ function deepEqual(val1, val2) {
     }
 
     // Object comparison.
-    if (typeof val1 === 'object' && typeof val2 === 'object') {
+    if (typeof val1 === 'object' && typeof val2 === 'object' && val1 !== null) {
-        const keys1 = Object.keys(val1);
+        const keys1 = Object.keys(val1), keys2 = Object.keys(val2);
-        const keys2 = Object.keys(val2);
         if (keys1.length !== keys2.length) {
             return false;
         }

utilities/javascript/graphTopoSort.js

@@ -32,4 +32,4 @@ function graphTopoSort(numberNodes, edges) {
     return order.length == numberNodes ? order : [];
 }
 
-console.log(graphTopoSort(3, [[0, 1], [0, 2]]))
+console.log(graphTopoSort(3, [[0, 1], [0, 2]]));

utilities/javascript/intToBin.js

@@ -0,0 +1,19 @@
+// 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');

utilities/javascript/intervalsIntersect.js

@@ -0,0 +1,17 @@
+// Interval: [start, end].
+function intervalsIntersect(a, b) {
+    return a[0] < b[1] && b[0] < a[1];
+}
+
+console.log(intervalsIntersect([1, 2], [3, 4]) === false);
+console.log(intervalsIntersect([1, 2], [2, 4]) === false);
+console.log(intervalsIntersect([1, 2], [1, 4]) === true);
+console.log(intervalsIntersect([1, 2], [0, 4]) === true);
+console.log(intervalsIntersect([1, 2], [0, 2]) === true);
+console.log(intervalsIntersect([1, 2], [0, 1.5]) === true);
+console.log(intervalsIntersect([3, 4], [1, 2]) === false);
+console.log(intervalsIntersect([2, 4], [1, 2]) === false);
+console.log(intervalsIntersect([1, 4], [1, 2]) === true);
+console.log(intervalsIntersect([0, 4], [1, 2]) === true);
+console.log(intervalsIntersect([0, 2], [1, 2]) === true);
+console.log(intervalsIntersect([0, 1.5], [1, 2]) === true);

utilities/javascript/intervalsMerge.js

@@ -0,0 +1,16 @@
+// 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])];
+}
+
+const deepEqual = require('./deepEqual');
+
+console.log(deepEqual(intervalsMerge([1, 2], [1, 4]), [1, 4]));
+console.log(deepEqual(intervalsMerge([1, 2], [0, 4]), [0, 4]));
+console.log(deepEqual(intervalsMerge([1, 2], [0, 2]), [0, 2]));
+console.log(deepEqual(intervalsMerge([1, 2], [0, 1.5]), [0, 2]));
+console.log(deepEqual(intervalsMerge([1, 4], [1, 2]), [1, 4]));
+console.log(deepEqual(intervalsMerge([0, 4], [1, 2]), [0, 4]));
+console.log(deepEqual(intervalsMerge([0, 2], [1, 2]), [0, 2]));
+console.log(deepEqual(intervalsMerge([0, 1.5], [1, 2]), [0, 2]));

utilities/javascript/matrixClone.js

@@ -0,0 +1,18 @@
+function matrixClone(matrix, defaultValue) {
+    return matrix.map(row => {
+        return defaultValue === undefined ? row.slice(0) : Array(row.length).fill(defaultValue);
+    });
+}
+
+const deepEqual = require('./deepEqual');
+
+// Test clone.
+const a = [[1, 2], [1, 4]];
+console.log(deepEqual(matrixClone(a), [[1, 2], [1, 4]]));
+a[0][0] = 4;
+console.log(deepEqual(matrixClone(a), [[1, 2], [1, 4]]) === false);
+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]]));

utilities/javascript/matrixTranspose.js

@@ -0,0 +1,11 @@
+function matrixTranspose(matrix) {
+    return matrix[0].map((col, i) => matrix.map(row => row[i]));
+}
+
+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]]));
+

utilities/javascript/matrixTraverse.js

@@ -0,0 +1,28 @@
+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);
+        }
+    }
+}