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  Given a string `s` which consists of lowercase or uppercase letters, return  _the length of the longest palindrome_  that can be built with those letters. Letters are case sensitive, for...

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[LeetCode] 16. 3Sum Closest

3

[请点击下方图片观看讲解视频](https://www.youtube.com/watch?v=g87mM5FJYqw) [Click below image to watch YouTube Video](https://www.youtube.com/watch?v=g87mM5FJYqw) [](https://www.youtube.com/watch?v=g87mM5FJYqw) Given an integer array `nums` of length `n` and an integer `target`, find three integers in `nums` such that the sum...

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[LeetCode] 327. Count of Range Sum

2

  Given an integer array `nums`, return the number of range sums that lie in `[lower, upper]` inclusive. Range sum `S(i, j)` is defined as the sum of the elements in ...

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[LeetCode] 215. Kth Largest Element in an Array

4

  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. Example 1: Input: [3,2,1,5,6,4]...

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[LeetCode] 148. Sort List

5

  Sort a linked list in  _O_ ( _n_  log  _n_ ) time using constant space complexity. Example 1: Input: 4->2->1->3 Output: 1->2->3->4 Example 2: Input: -1->5->3->4->0 Output: -1->0->3->4->5   常见排序方法有很多，插入排序，选择排序，堆排序，快速排序，冒泡排序，归并排序，桶排序等等。。它们的时间复杂度不尽相同，而这里题目限定了时间必须为O(nlgn)，符合要求只有快速排序，归并排序，堆排序，而根据单链表的特点，最适于用归并排序。为啥呢？这是由于链表自身的特点决定的，由于不能通过坐标来直接访问元素，所以快排什么的可能不太容易实现（但是被评论区的大神们打脸，还是可以实现的），堆排序的话，如果让新建结点的话，还是可以考虑的，若只能交换结点，最好还是不要用。而归并排序（又称混合排序）因其可以利用递归来交换数字，天然适合链表这种结构。归并排序的核心是一个 merge()...

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You are given a string `s` containing lowercase letters and an integer `k`. You need to : * First, change some characters of `s` to other lowercase English letters. *...

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[LeetCode] 153. Find Minimum in Rotated Sorted Array

1

  Suppose an array of length `n` sorted in ascending order is rotated between `1` and `n` times. For example, the array `nums = [0,1,2,4,5,6,7]` might become: * `[4,5,6,7,0,1,2]` if it...

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[LeetCode] 772. Basic Calculator III

7

  Implement a basic calculator to evaluate a simple expression string. The expression string may contain open `(` and closing parentheses `)`, the plus `+` or minus sign `-`, non-negative integers...

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Return the length of the shortest, non-empty, contiguous subarray of `A` with sum at least `K`. If there is no non-empty subarray with sum at least `K`, return `-1`. Example...

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[LeetCode] 162. Find Peak Element

1

  A peak element is an element that is strictly greater than its neighbors. Given an integer array `nums`, find a peak element, and return its index. If the array contains...

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