Unique Binary Search Trees I && II 解法请见：https://yanjia.li/zh/2019/02/… Given n, how many structu…

题目 Reverse digits of an integer. Example1: x = 123, return 321 Example2: x = -123, return -321 思路分析： Have you …

题目： Given an array of strings, return all groups of strings that are anagrams. Note: All inputs will be in low…

题目地址：https://leetcode-cn.com/probl…题目描述：给定一棵二叉树，返回所有重复的子树。对于同一类的重复子树，你只需要返回其中任意一棵的根结点即可。 两棵树重复是指它们具有相同的结…

  Let f(x) be the number of zeroes at the end of x!. (Recall that x! = 1 * 2 * 3 * ..…

题目： Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following…

Given an array of integers, return indices of the two numbers such that they add up to a specific target. You …

77. Combinations 题目 Given two integers n and k, return all possible combinations of k numbers out of 1 ... n. …

  Remove the minimum number of invalid parentheses in order to make the input string valid. Return all po…

  Implement a data structure supporting the following operations:   Inc(Key) – Inserts a new k…

  A magical string S consists of only ‘1’ and ‘2’ and obeys the followi…

  Given an array with n integers, you need to find if there are triplets (i, j, k) which satisfies follow…