题目： Given a binary tree, determine if it is a valid binary search tree (BST). Assume a BST is defined as follo…

Wildcard Matching Implement wildcard pattern matching with support for ‘?’ and ‘*’. &#…

leetcode – 33. Search in Rotated Sorted Array – Medium descrition Suppose an array sorted in ascen…

929. Unique Email Addresses 题目链接 929. Unique Email Addresses 题目分析 题目要求过滤重复的邮箱地址。最终返回不重复的用户名个数。 过滤规则是：邮箱名中的.要被忽…

题意：给你一个正数，判断这个正数是不是完全平方数。 解题思路：“完全平方数” = 1 + 3 + 5 + 7 + 9 +… 1^2 = 1； 2^2 = 1 + 3 = (1 + 3) / 2 = 2 + 2…

  Reverse a linked list from position m to n. Do it in one-pass. Note: 1 ≤ m&nbs…

  Given an integer n, return the number of trailing zeroes in n!. Note: Your solution shou…

  This is a follow up of Shortest Word Distance. The only difference is now word1 could be the same as wo…

  Given two integer arrays A and B, return the maximum length of an subarray that appears in both arrays.…

  Given a string S, check if the letters can be rearranged so that two characters that are adjacent …

题目： Say you have an array for which the ith element is the price of a given stock on day i. Des…

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money …