Articles
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154 - Find Minimum in Rotated Sorted Array II
Suppose a sorted array is rotated at some pivot unknown to you beforehand. (i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2). Find the minimum element. The array may contain duplicates.
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153 - Find Minimum in Rotated Sorted Array
Suppose a sorted array is rotated at some pivot unknown to you beforehand. (i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2). Find the minimum element.
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81 - Search in Rotated Sorted Array II
Follow up for “Search in Rotated Sorted Array”: What if duplicates are allowed? Would this affect the run-time complexity? How and why? Write a function to determine if a given target is in the array.
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33 - Search in Rotated Sorted Array
Suppose a sorted array is rotated at some pivot unknown to you beforehand. (i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2). You are given a target value to search. If found in the array return its index, otherwise return -1. You may assume no duplicate exists in the array.
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162 - Find Peak Element
A peak element is an element that is greater than its neighbors. Given an input array where num[i] != num[i+1], find a peak element and return its index. The array may contain multiple peaks, in that case return the index to any one of the peaks is fine. You may imagine that num[-1] = num[n] = -inf. For example, in array [1, 2, 3, 1], 3 is a peak element and your function should return the index number 2.
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74 - Search a 2D Matrix
Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: Integers in each row are sorted from left to right. The first integer of each row is greater than the last integer of the previous row.
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278 - First Bad Version
The code base version is an integer start from 1 to n. One day, someone committed a bad version in the code case, so it caused this version and the following versions are all failed in the unit tests. Find the first bad version.
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34 - Search for a Range
Given a sorted array of integers, find the starting and ending position of a given target value. Your algorithm’s runtime complexity must be in the order of O(log n). If the target is not found in the array, return [-1, -1].
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35 - Search Insert Position
Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order. You may assume NO duplicates in the array.
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Binary Search
For a given sorted array (ascending order) and a target number, find the first index of this number in O(log n) time complexity. If the target number does not exist in the array, return -1.
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215 - Kth Largest Element in an Array
Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element. For example, given [3,2,1,5,6,4] and k = 2, return 5.
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Partition Array by Odd and Even
Partition an integers array into odd number first and even number second.
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Median of unsorted array
Given a unsorted array with integers, find the median of it. A median is the middle number of the array after it is sorted. If there are even numbers in the array, return the N/2 th number after sorted.
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Merge Sorted Array II
Merge two given sorted integer array A and B into a new sorted integer array.
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88 - Merge Sorted Array
Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.
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80 - Remove Duplicates from Sorted Array II
Follow up for “Remove Duplicates”: What if duplicates are allowed at most twice?
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26 - Remove Duplicates from Sorted Array
Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length. Do not allocate extra space for another array, you must do this in place with constant memory. For example, Given input array nums = [1,1,2], Your function should return length = 2, with the first two elements of nums being 1 and 2 respectively. It doesn’t matter what you leave beyond the new length.
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16 - 3Sum Closest
Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.
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18 - 4Sum
Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.
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15 - 3Sum
Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.
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41 - First Missing Positive
Given an unsorted integer array, find the first missing positive integer.
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31 - Partition Array
Given an array nums of integers and an int k, partition the array (i.e move the elements in “nums”) such that: All elements < k are moved to the leff. All elements >= k are moved to the right Return the partitioning index, i.e the first index i nums[i] >= k.
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238 - Product of Array Exclude Itself
Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].
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Recover Rotated Sorted Array
Given a rotated sorted array, recover it to sorted array in-place.
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139 - Subarray Sum Closest
Given an integer array, find a subarray with sum closest to zero. Return the indexes of the first number and last number.
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139 - Subarray Sum II
Given an integer array, find a subarray where the sum of numbers is between two given interval. Your code should return the number of possible answer.
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Subarray Sum K
Given an nonnegative integer array, find a subarray where the sum of numbers is k. Your code should return the index of the first number and the index of the last number.
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138 - Subarray Sum
Given an integer array, find a subarray where the sum of numbers is zero. Your code should return the index of the first number and the index of the last number.
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27 - Remove Element
Given an array and a value, remove all instances of that value in place and return the new length. The order of elements can be changed. It doesn’t matter what you leave beyond the new length.
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38 - Count and Say
The count-and-say sequence is the sequence of integers beginning as follows:
