Given an array of 4 digits, return the largest 24 hour time that can be made. The smallest 24 hour time is 00:00, and the largest is 23:59.  Starting from 00:00, a time is larger if more time has elapsed since midnight. Return the answer as a string…

Given an array A of positive lengths, return the largest perimeter of a triangle with non-zero area, formed from 3 of these lengths. If it is impossible to form any triangle of non-zero area, return 0. Example 1: Input: [2,1,2] Output: 5 Example 2: I…

In a deck of cards, every card has a unique integer.  You can order the deck in any order you want. Initially, all the cards start face down (unrevealed) in one deck. Now, you do the following steps repeatedly, until all cards are revealed: Take the…

For a binary tree T, we can define a flip operation as follows: choose any node, and swap the left and right child subtrees. A binary tree X is flip equivalent to a binary tree Y if and only if we can make X equal to Y after some number of flip opera…

LeetCode Weekly Contest 8 415. Add Strings User Accepted: 765 User Tried: 822 Total Accepted: 789 Total Submissions: 1844 Difficulty: Easy Given two non-negative numbers num1 and num2 represented as string, return the sum of num1 and num2. Note: The…

leetcode weekly contest 43 leetcode649. Dota2 Senate leetcode649.Dota2 Senate 思路: 模拟规则round by round. class Solution { public: string predictPartyVictory(string senate) { int len = senate.size(); int r = 0; int d = 0; int i = 0; while(1) { if(senate[…

LeetCode Weekly Contest 23 1. Reverse String II Given a string and an integer k, you need to reverse the first k characters for every 2k characters counting from the start of the string. If there are less than k characters left, reverse all of them.…

Weekly Contest 86 A:840. 矩阵中的幻方 3 x 3 的幻方是一个填充有从 1 到 9 的不同数字的 3 x 3 矩阵,其中每行,每列以及两条对角线上的各数之和都相等. 给定一个由整数组成的 N × N 矩阵,其中有多少个 3 × 3 的 “幻方” 子矩阵?(每个子矩阵都是连续的). 直接模拟即可,本来是签到题,由于粗心,浪费了时间. class Solution { public: int numMagicSquaresInside(vector<vector<int&…

链接:https://leetcode.com/contest/leetcode-weekly-contest-33/ A.Longest Harmonious Subsequence 思路:hash加查找 class Solution { public: int findLHS(vector<int>& nums) { if (nums.empty()) ; ; int len = nums.size(); unordered_map<int, int> hash(len…

[题目链接]:https://leetcode.com/contest/leetcode-weekly-contest-26/problems/split-array-with-equal-sum/ [题意] 让你把一段序列去掉3个元素,然后分成4个部分; 要求这4个部分的和相同; 问你可不可能; [题解] 先枚举要删除的3个元素中的中间那个元素j; 然后把整个序列分成左边和右边两个部分; 然后再左边的序列中枚举i; 然后把0..j-1分成0..i-1和i+1..j-1两个部分; 然后看这两个部…