leetcode 解题思路

There arencities. Some of them are connected, while some are not. If cityais connected directly with cityb, and citybis connected directly with cityc, then cityais connected indirectly with cityc.Aprovinceis a group of directly or indirectly...

In this problem, a tree is anundirectedgraph 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 additi...

We havencities labeled from1ton. Two different cities with labelsxandyare directly connected by a bidirectional road if and only ifxandyshare a common divisorstrictly greaterthan somethreshold. More formally, cities with labelsxandyhave...

You are given an arraypointsrepresenting integer coordinates of some points on a 2D-plane, wherepoints[i] = [xi, yi].The cost of connecting two points[xi, yi]and[xj, yj]is themanhattan distancebetween them:|xi- xj| + |yi- yj|, where|val|den...

Alice and Bob have an undirected graph ofnnodesand 3 types of edges:Type 1: Can be traversed by Alice only. Type 2: Can be traversed by Bob only. Type 3: Can by traversed by both Alice and Bob.Given an arrayedgeswhereedges[i] = [typei, ui, vi]r...

Given an arrayarrthat represents a permutation of numbers from1ton. You have a binary string of sizenthat initially has all its bits set to zero.At each stepi(assuming both the binary string andarrare 1-indexed) from1ton, the bit at positio...

On a 2D plane, we place stones at some integer coordinate points. Each coordinate point may have at most one stone.Now, amoveconsists of removing a stonethat shares a column or row with another stone on the grid.What is the largest possible number ...

In this problem, a rooted tree is adirectedgraph 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, excep...

In a network of nodes, each nodeiis directly connected to another nodejif and only ifgraph[i][j] = 1.Some nodesinitialare initially infected by malware. Whenever two nodes are directly conne...

Given a non-emptyarray of unique positive integersA, consider the following graph:There areA.lengthnodes, labelledA[0]toA[A.length - 1]; There is an edge betweenA[i]andA[j]if and only if...

There areNcities numbered from 1 toN.You are givenconnections, where eachconnections[i] = [city1, city2, cost]represents the cost to connectcity1andcity2together. (Aconnectionis bidirec...

Given two sentenceswords1, words2(each represented as an array of strings), and a list of similar word pairspairs, determine if two sentences are similar.For example,words1 = ["great", "acting",...

Givennnodes labeled from0ton - 1and a list of undirected edges (each edge is a pair of nodes), write a function to find the number of connected components in an undirected graph.Example 1:

There areNrooms and you start in room0. Each room has a distinct number in0, 1, 2, ..., N-1, and each room may havesome keys to access the next room.Formally, each roomihas a list of keysr...

There arenhouses in a village. We want to supply water for all the houses by building wells and laying pipes.For each housei, we can either build a well inside it directly with costwells[i], or ...

Amazon sells books, every book has books which are strongly associated with it. Given ListA and ListB,indicates thatListA [i]is associated withListB [i]which represents the book and associated boo...

Given a listaccounts, each elementaccounts[i]is a list of strings, where the first elementaccounts[i][0]is aname, and the rest of the elements areemailsrepresenting emails of the account.Now...

Connecting Graph给一个图中的n个节点, 记为1到n. 在开始的时候图中没有边。你需要完成下面两个方法:connect(a, b), 添加连接节点a,b的边. query(a, b), 检验两个节点是否联通思路：Union Find模板要会背诵；public class ConnectingGraph { private class Unio...

There is a list composed by sets. If two sets have the same elements, merge them. In the end, there are several sets left.ExampleExample 1:Input :list = [[1,2,3],[3,9,7],[4,5,10]]Output:2 .Ex...

Given a n,m which means the row and column of the 2D matrix and an array of pair A( size k). Originally, the 2D matrix is all 0 which means there is only sea in the matrix. The list pair has k operato...

Given a list of Connections, which is the Connection class (the city name at both ends of the edge and a cost between them), find edges that can connect all the cities and spend the least amount.Retu...

Givennnodes labeled from0ton - 1and a list ofundirectededges (each edge is a pair of nodes), write a function to check whether these edges make up a valid tree.ExampleExample 1:Input: n...

Givennnodes in a graph labeled from1ton. There is no edges in the graph at beginning.You need to support the following method:connect(a, b), an edge to connect node a and node b query(), Ret...

Givennnodes in a graph labeled from1ton. There is no edges in the graph at beginning.You need to support the following method:connect(a, b), add an edge to connect nodeaand node b`. query(...

Givennnodes in a graph labeled from1ton. There is no edges in the graph at beginning.You need to support the following method:connect(a, b), an edge to connect node a and node b query(a), Re...

There areNstudents in a class. Some of them are friends, while some are not. Their friendship is transitive in nature. For example, if A is adirectfriend of B, and B is adirectfriend of C, then ...

今天终于完成了第一个Union-Find的assignment，之前觉得特别的难，可是最后自己也搞定了。而且是100%满分。自己后来plot了一下自己的分数，也许这就是学习曲线吧。刚开始不会，到后来中期显著提高，但是要到100%，那就要经历更多的波折，甚至是下降都有可能。最后才能达到100%满分。我觉得最有用的还是下面这段源代码：/************************...