Yangshun Tay
7 years ago
parent
7247dbcaf7
commit
b92118eb31
@ -1,37 +0,0 @@
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---
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id: 1
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title: Histogram Stars
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topics: [array]
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difficulty: easy
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---
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## Question
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```
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'''
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Given an array of integers, print out a histogram using the array. Include a base layer (all stars)
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[5, 4, 0, 3, 4, 1] will result in the following:
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******
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*****
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*
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****
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*****
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**
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'''
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```
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## Follow Up
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```
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Print out a vertical version of the histogram.
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*
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** *
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** **
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** **
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** ***
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******
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'''
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```
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@ -1,56 +0,0 @@
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---
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id: 2
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title: Matrix Islands
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topics: [array, depth-first-search, matrix]
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difficulty: easy
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source:
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- https://leetcode.com/problems/number-of-islands/
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- https://leetcode.com/problems/max-area-of-island/
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- https://leetcode.com/problems/number-of-distinct-islands/
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---
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## Question
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```
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'''
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Given a matrix of 0s and 1s, count the number of islands present.
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[[0,0,1],
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[0,0,0],
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[0,1,1]]
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Answer: 2
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'''
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```
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## Follow Up
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```
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Given a matrix of 0s and 1s, find the size of the largest island present.
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'''
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[[0,0,1],
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[0,0,0],
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[0,1,1]]
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Answer: 2
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```
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## Follow Up II
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```
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Given a matrix of 0s and 1s, find the number of unique islands present present.
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'''
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[[1,0,1,0],
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[1,0,0,0],
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[0,1,1,0]]
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Answer: 3
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[[1,1,0,1],
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[0,0,0,0],
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[0,1,1,0]]
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Answer: 2
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```
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@ -1,40 +0,0 @@
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---
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id: 3
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title: K Smallest Elements from Two Sorted Arrays
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topics: [array]
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difficulty: easy
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---
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## Question
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```
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'''
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Find the k smallest elements from two sorted arrays of integers.
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Input: [1, 2, 3, 4, 5], [2, 3, 4], k = 3
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Output: [1, 2, 2]
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'''
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```
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## Time Complexities
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- Bad:
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- Time: O((n + m)log(n + m))
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- Good:
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- Time: O(k)
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## Sample Answers
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```py
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def k_smallest(A, B, k):
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res = []
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a = b = 0
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while a < len(A) and b < len(B) and (a + b) < k:
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if A[a] < B[b]:
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res.append(A[a])
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a += 1
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else:
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res.append(B[b])
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b += 1
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return res + A[a:k - b] + B[b:k - a]
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```
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---
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id: 4
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title: Synonyms
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topics: [graph]
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difficulty: medium
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---
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## Question
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```
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'''
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Given a list of synonym pairs, determine if two words are synonymous.
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Synonyms have a symmetric and transitive relation. i.e. if a <-> b and b <-> c, a <-> c.
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Input:
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[["computer", "laptop"]]
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"computer"
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"laptop"
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Output: true
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Input:
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[["computer", "laptop"], ["laptop", "pc"]]
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"computer"
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"pc"
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Output: true
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Input:
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[["computer", "laptop"], ["laptop", "pc"], ["tablet", "iPad"]]
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"computer"
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"iPad"
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Output: false
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'''
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```
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@ -1,33 +0,0 @@
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---
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id: 5
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title: Longest Consecutive Set of Numbers
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topics: [graph]
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difficulty: hard
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source: https://leetcode.com/problems/longest-consecutive-sequence/
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---
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## Question
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```
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'''
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Given an array of integers, find the size of the largest set of consecutive numbers present in the array.
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Input: [100, 4, 200, 1, 3, 2]
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Output: 4 because {1, 2, 3, 4}
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'''
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```
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## Sample Answers
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```py
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def longest_consecutive(nums):
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nums = set(nums)
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best = 0
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for x in nums:
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if x - 1 not in nums:
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y = x + 1
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while y in nums:
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y += 1
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best = max(best, y - x)
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return best
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```
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---
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id: 6
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title: String Compression and Decompression
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topics: [string]
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difficulty: easy
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---
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## Question
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```
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'''
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Given a string, compress it by grouping repeated characters. The length after
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compression must always be smaller than or equal to the original string.
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'aaabbccc' => 'a3b2c3'
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'''
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```
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```
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'''
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Given the above compressed string, decompress to obtain the original string.
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'a3b2c3' => 'aaabbccc'
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'''
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```
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@ -1,21 +0,0 @@
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---
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id: 7
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title: Biggest Number After Swap
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topics: [math]
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difficulty: medium
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source: https://leetcode.com/problems/maximum-swap/
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---
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## Question
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```
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'''
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Given a non-negative integer, find the maximum possible number if you can swap two digits at most once.
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2736 => 7236
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'''
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```
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## Follow Up
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- What if the given integer can be negative?
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@ -1,19 +0,0 @@
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---
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id: 8
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title: Pivot Index
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topics: [array]
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difficulty: easy
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source: https://leetcode.com/problems/find-pivot-index/
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---
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## Question
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```
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'''
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Given an array of integers, return the pivot index of this array.
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A pivot index is the index where the sum of the numbers to its left is equal to the sum of the numbers to its right:
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[7, 2, 3, 4] => 1
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'''
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```
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@ -1,18 +0,0 @@
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---
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id: 9
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title: Move Zeroes
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topics: [array]
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difficulty: easy
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source: https://leetcode.com/problems/move-zeroes/
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---
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## Question
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```
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'''
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Given an array of integers, write a function to move all zeroes to the end of it while
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maintaining the relative order of the non-zero elements.
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[0, 1, 0, 3, 12] => [1, 3, 12, 0, 0].
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'''
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```
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