package UnionFind; import java.util.ArrayList; import java.util.LinkedList; import java.util.List; public class UnionFindProblem { public static void main(String[] args) { // TODO Auto-generated method stub } /* * 网上查了一下:http://blog.csdn.net/dm_vince…

A 2d grid map of m rows and n columns is initially filled with water. We may perform an addLand operation which turns the water at position (row, col) into a land. Given a list of positions to operate, count the number of islands after each addLand o…

Union Find算法基础 Union Find算法用于处理集合的合并和查询问题,其定义了两个用于并查集的操作: Find: 确定元素属于哪一个子集,或判断两个元素是否属于同一子集 Union: 将两个子集合并为一个子集 并查集是一种树形的数据结构,其可用数组或unordered_map表示: Find操作即查找元素的root,当两元素root相同时判定他们属于同一个子集:Union操作即通过修改元素的root(或修改parent)合并子集,下面两个图展示了id[6]由6修改为9的变化:   …

Given an unsorted array of integers, find the length of the longest consecutive elements sequence. Your algorithm should run in O(n) complexity. Example: Input: [100, 4, 200, 1, 3, 2] Output: 4 Explanation: The longest consecutive elements sequence i…

You are given an integer array of unique positive integers nums. Consider the following graph: There are nums.length nodes, labeled nums[0] to nums[nums.length - 1], There is an undirected edge between nums[i] and nums[j] if nums[i] and nums[j] share…

A 2d grid map of m rows and n columns is initially filled with water. We may perform an addLand operation which turns the water at position (row, col) into a land. Given a list of positions to operate, count the number of islands after each addLand o…

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. For example: Given n = 5 and edges = [[0, 1], [0, 2], [0, 3], [1, 4]], return tru…

Write a SQL query to get the second highest salary from the Employee table. +----+--------+ | Id | Salary | +----+--------+ | 1 | 100 | | 2 | 200 | | 3 | 300 | +----+--------+ For example, given the above Employee table, the second highest salary is …

原题链接在这里:https://leetcode.com/problems/number-of-connected-components-in-an-undirected-graph/ 题目: 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 com…

原题链接在这里:https://leetcode.com/problems/graph-valid-tree/ 题目: 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. For example: Given n…

题目来源:https://leetcode.com/problems/median-of-two-sorted-arrays/ There are two sorted arrays nums1 and nums2 of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)). 解题思路: 题目是这样的:给…

(http://leetcode.com/2011/01/find-k-th-smallest-element-in-union-of.html) Given two sorted arrays A, B of size m and n respectively. Find the k-th smallest element in the union of A and B. You can assume that there are no duplicate elements. O(lg m +…

There are N students in a class. Some of them are friends, while some are not. Their friendship is transitive in nature. For example, if A is a direct friend of B, and B is a direct friend of C, then A is an indirect friend of C. And we defined a fri…

N couples sit in 2N seats arranged in a row and want to hold hands. We want to know the minimum number of swaps so that every couple is sitting side by side. A swap consists of choosing any two people, then they stand up and switch seats. The people…

Given an undirected graph, return true if and only if it is bipartite. Recall that a graph is bipartite if we can split it's set of nodes into two independent subsets A and B such that every edge in the graph has one node in A and another node in B.…

In this problem, a rooted tree is a directed graph such that, there is exactly one node (the root) for which all other nodes are descendants of this node, plus every node has exactly one parent, except for the root node which has no parents. The give…

Given an array A (index starts at 1) consisting of N integers: A1, A2, ..., AN and an integer B. The integer Bdenotes that from any place (suppose the index is i) in the array A, you can jump to any one of the place in the array A indexed i+1, i+2, ……

Given two sentences words1, words2 (each represented as an array of strings), and a list of similar word pairs pairs, determine if two sentences are similar. For example, words1 = ["great", "acting", "skills"] and words2 = [&…

Given a list accounts, each element accounts[i] is a list of strings, where the first element accounts[i][0] is a name, and the rest of the elements are emails representing emails of the account. Now, we would like to merge these accounts. Two accoun…

In this problem, a tree is an undirected graph that is connected and has no cycles. The given input is a graph that started as a tree with N nodes (with distinct values 1, 2, ..., N), with one additional edge added. The added edge has two different v…

Given a set of N people (numbered 1, 2, ..., N), we would like to split everyone into two groups of any size. Each person may dislike some other people, and they should not go into the same group. Formally, if dislikes[i] = [a, b], it means it is not…

We have a grid of 1s and 0s; the 1s in a cell represent bricks.  A brick will not drop if and only if it is directly connected to the top of the grid, or at least one of its (4-way) adjacent bricks will not drop. We will do some erasures sequentially…

A quadtree is a tree data in which each internal node has exactly four children: topLeft, topRight, bottomLeft and bottomRight. Quad trees are often used to partition a two-dimensional space by recursively subdividing it into four quadrants or region…

原题链接在这里:https://leetcode.com/problems/friend-circles/description/ 题目: There are N students in a class. Some of them are friends, while some are not. Their friendship is transitive in nature. For example, if A is a direct friend of B, and B is a direc…

1.Two Sum Given an array of integers, return indices of the two numbers such that they add up to a specific target. You may assume that each input would have exactly one solution, and you may not use the same element twice. 使用hash public int[] twoSum…

原题链接在这里:https://leetcode.com/problems/number-of-connected-components-in-an-undirected-graph/ 题目: 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 com…

原题链接在这里:https://leetcode.com/problems/number-of-islands-ii/ 题目: A 2d grid map of m rows and n columns is initially filled with water. We may perform an addLand operation which turns the water at position (row, col) into a land. Given a list of positi…

https://oj.leetcode.com/problems/reorder-list/ 将一个链表重新排序,比如 1 2 3 4 5,变成 1 5 2 4 3 1.找到中间节点 mid 2.将链表分成两部分 head,head2 3.将head2 逆序 4.将head head2,再合并成一个链表 class Solution { public: void reorderList(ListNode *head) { //0 elements, 1 elements, 2 elements…

★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★➤微信公众号:山青咏芝(shanqingyongzhi)➤博客园地址:山青咏芝(https://www.cnblogs.com/strengthen/)➤GitHub地址:https://github.com/strengthen/LeetCode➤原文地址:https://www.cnblogs.com/strengthen/p/10414498.html ➤如果链接不是山青咏芝的博客园地址,则可能是爬取作者的文章…

写的有点晚了. 我每次都是先看一下这里http://bookshadow.com/leetcode/的思路,然后再开始写我自己的. 1. 521. Longest Uncommon Subsequence I 说实话,看完就懵逼了,这怎么做,难道是dp,后仔细一想,不对啊,很简单啊. 只要2个字符串不相等,返回长度较长的那个就行了. 刚开始,考虑,如果其中之一为空串,我返回的-1,不知道怎么想的.这显然是错的. class Solution { public: int findLUSlength…