LeetCode-34-Search-for-a-Range Given an array of integers sorted in ascending order, 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]. 在一个排序的数组中找到出现这个值的起点和重点。很容

LeetCode-32-Longest-Valid-Parentheses Given a string containing just the characters ‘(’ and ‘)’, find the length of the longest valid (well-formed) parentheses substring. For “(()”, the longest valid parentheses substring is “()”, which has length = 2. Another example is “)()())”, where the longest valid parentheses substring is “()()”, which has length = 4. 表示这是一道没有看懂题目的题，看到题

LeetCode-31-Next-Permutation Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers. If such arrangement is not possible, it must rearrange it as the lowest possible order (ie, sorted in ascending order). The replacement must be in-place, do not allocate extra memory. 这个排序主要是有两种情况，一个是类似于3 1 2 这样的

Given a linked list, remove the nth node from the end of list and return its head. For example, Given linked list: 1->2->3->4->5, and n = 2. After removing the second node from the end, the linked list becomes 1->2->3->5. 这个题目之前在剑指offer上就有，记得当时的方法是：采用两

23. Merge k Sorted Lists Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity. 这个题乍一看只是对链表的一个排序，因为是很多个链表，所以很简单的想法就是将整个数组里面的两个链表

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. Note: The solution set must not contain duplicate triplets. For example, given array S = [-1, 0, 1, 2, -1, -4], A solution set is: [ [-1, 0, 1], [-1, -1,