摘要：看不懂 union find 的代码 https://leetcode.com/problems/bricks-falling-when-hit/discuss/141229/JAVA-Simple-DFS-16ms-reversely-add-bricks-back Very clever idea using -1 to stop visiting the points already ... 阅读全文

摘要：each time, can only change one of the four positions. And for each position, can only change either + 1 , or - 1 use "+ 10 mod 10" to guarentee a posi 阅读全文

摘要：Given n nodes labeled from 0 to n-1 and a list of undirected edges (each edge is a pair of nodes), write a function to check whether these edges make up a valid tree. Example 1: Input: n = 5, and edg... 阅读全文

摘要：https://leetcode.com/problems/minimum-height-trees/discuss/76055/Share-some-thoughts For a undirected graph with tree characteristics, we can choose any node as the root. The result graph is then a... 阅读全文

摘要：Given a matrix consists of 0 and 1, find the distance of the nearest 0 for each cell. The distance between two adjacent cells is 1. Example 1: Input: 0 0 0 0 1 0 0 0 0 Output: 0 0 0 0 1 0 0 0 0 Exa... 阅读全文

摘要：There is a ball in a maze with empty spaces and walls. The ball can go through empty spaces by rolling up, down, left or right, but it won't stop roll 阅读全文

摘要：There is a ball in a maze with empty spaces and walls. The ball can go through empty spaces by rolling up, down, left or right, but it won't stop roll 阅读全文

摘要：Example 2: 阅读全文

摘要：Given a 2D board containing 'X' and 'O' (the letter O), capture all regions surrounded by 'X'. A region is captured by flipping all 'O's into 'X's in that surrounded region. Example: X X X X X O O X ... 阅读全文

摘要：We have a list of bus routes. Each routes[i] is a bus route that the i-th bus repeats forever. For example if routes[0] = [1, 5, 7], this means that t 阅读全文

摘要：Given a set of N people (numbered 1, 2, ..., N), we would like to split everyone into two groups of anysize. Each person may dislike some other people 阅读全文

摘要：301. Remove Invalid Parentheses Remove the minimum number of invalid parentheses in order to make the input string valid. Return all possible results. Note: The input string may contain letters oth... 阅读全文

摘要：Given the head of a graph, return a deep copy (clone) of the graph. Each node in the graph contains a label (int) and a list (List[UndirectedGraphNode 阅读全文

摘要：Given a matrix that is filled with ‘O’, ‘G’, and ‘W’ where ‘O’ represents open space, ‘G’ represents guards and ‘W’ represents walls in a Bank. Replac 阅读全文

摘要：126. Word Ladder II Given two words (beginWord and endWord), and a dictionary's word list, find all shortest transformation sequence(s) from beginWord to endWord, such that: 1. Only one letter can... 阅读全文

摘要：Given two words (beginWord and endWord), and a dictionary's word list, find the length of shortest transformation sequence from beginWord to endWord, 阅读全文

摘要：Given an m x n matrix of non-negative integers representing the height of each unit cell in a continent, the "Pacific ocean" touches the left and top 阅读全文

摘要：An image is represented by a 2-D array of integers, each integer representing the pixel value of the image (from 0 to 65535). Given a coordinate (sr, 阅读全文

摘要：You want to build a house on an empty land which reaches all buildings in the shortest amount of distance. You can only move up, down, left and right. 阅读全文

摘要：Given n nodes labeled from 0 to n - 1 and a list of undirected edges (each edge is a pair of nodes), write a function to find the number of connected 阅读全文