原题链接在这里:https://leetcode.com/problems/all-paths-from-source-lead-to-destination/

题目:

Given the edges of a directed graph, and two nodes source and destination of this graph, determine whether or not all paths starting from source eventually end at destination, that is:

  • At least one path exists from the source node to the destination node
  • If a path exists from the source node to a node with no outgoing edges, then that node is equal to destination.
  • The number of possible paths from source to destination is a finite number.

Return true if and only if all roads from source lead to destination.

Example 1:

Input: n = 3, edges = [[0,1],[0,2]], source = 0, destination = 2
Output: false
Explanation: It is possible to reach and get stuck on both node 1 and node 2.

Example 2:

Input: n = 4, edges = [[0,1],[0,3],[1,2],[2,1]], source = 0, destination = 3
Output: false
Explanation: We have two possibilities: to end at node 3, or to loop over node 1 and node 2 indefinitely.

Example 3:

Input: n = 4, edges = [[0,1],[0,2],[1,3],[2,3]], source = 0, destination = 3
Output: true

Example 4:

Input: n = 3, edges = [[0,1],[1,1],[1,2]], source = 0, destination = 2
Output: false
Explanation: All paths from the source node end at the destination node, but there are an infinite number of paths, such as 0-1-2, 0-1-1-2, 0-1-1-1-2, 0-1-1-1-1-2, and so on.

Example 5:

Input: n = 2, edges = [[0,1],[1,1]], source = 0, destination = 1
Output: false
Explanation: There is infinite self-loop at destination node.

Note:

  1. The given graph may have self loops and parallel edges.
  2. The number of nodes n in the graph is between 1 and 10000
  3. The number of edges in the graph is between 0 and 10000
  4. 0 <= edges.length <= 10000
  5. edges[i].length == 2
  6. 0 <= source <= n - 1
  7. 0 <= destination <= n - 1

题解:

There are 2 cases it should return false.

case 1: it encounters a node that has no outgoing edges, but it is not destination.

case 2: it has cycle.

Otherwise, it returns true.

Could iterate graph with BFS. When indegree of a node becomes negative, then ther is cycle.

Time Complexity: O(n+e). e = edges.length.

Space: O(n+e).

AC Java:

 class Solution {
public boolean leadsToDestination(int n, int[][] edges, int source, int destination) {
Set<Integer> [] graph = new Set[n]; for(int i = 0; i<n; i++){
graph[i] = new HashSet<Integer>();
} int [] inDegrees = new int[n];
for(int [] edge : edges){
graph[edge[0]].add(edge[1]);
inDegrees[edge[1]]++;
} LinkedList<Integer> que = new LinkedList<Integer>();
que.add(source); while(!que.isEmpty()){
int cur = que.poll();
if(graph[cur].size() == 0 && cur != destination){
return false;
} for(int nei : graph[cur]){
if(inDegrees[nei] < 0){
return false;
} inDegrees[nei]--; que.add(nei);
}
} return true;
}
}

Could iterate by DFS too.

If current node has been visited within current DFS, then there is cycle.

When traversing all the nodes, make current node as done.

Time Complexity: O(n+e).

Space: O(n+e).

AC Java:

 class Solution {
public boolean leadsToDestination(int n, int[][] edges, int source, int destination) {
Set<Integer> [] graph = new Set[n];
for(int i = 0; i<n; i++){
graph[i] = new HashSet<Integer>();
} for(int [] edge : edges){
graph[edge[0]].add(edge[1]);
} return dfs(source, destination, graph, new int[n]);
} private boolean dfs(int cur, int destination, Set<Integer> [] graph, int [] visited){
if(visited[cur] != 0){
return visited[cur] == 2;
} if(graph[cur].size() == 0){
return cur == destination;
} visited[cur] = 1;
for(int nei : graph[cur]){
if(!dfs(nei, destination, graph, visited)){
return false;
}
} visited[cur] = 2;
return true;
}
}

LeetCode 1059. All Paths from Source Lead to Destination的更多相关文章

  1. LeetCode 797. All Paths From Source to Target

    题目链接:https://leetcode.com/problems/all-paths-from-source-to-target/description/ Given a directed, ac ...

  2. 【leetcode】All Paths From Source to Target

    题目如下: Given a directed, acyclic graph of N nodes. Find all possible paths from node 0 to node N-1, a ...

  3. LeetCode 63. Unique Paths II不同路径 II (C++/Java)

    题目: A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below). ...

  4. [LeetCode] 62. Unique Paths 唯一路径

    A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below). The ...

  5. Data Flow ->> Raw File Source & Raw File Destination

    Raw File Source & Raw File Destination一般用在当有某个package在导入数据或者处理数据需要花费非常长的时间的情况下,可以通过把一些处理好的数据先存到r ...

  6. [LeetCode] All Paths From Source to Target 从起点到目标点到所有路径

    Given a directed, acyclic graph of N nodes.  Find all possible paths from node 0 to node N-1, and re ...

  7. 【LeetCode】797. All Paths From Source to Target 解题报告(Python & C++)

    作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 回溯法 日期 题目地址:https://leetco ...

  8. 75th LeetCode Weekly Contest All Paths From Source to Target

    Given a directed, acyclic graph of N nodes.  Find all possible paths from node 0 to node N-1, and re ...

  9. 【leetcode】797. All Paths From Source to Target

    Given a directed acyclic graph (DAG) of n nodes labeled from 0 to n - 1, find all possible paths fro ...

随机推荐

  1. JAVA知识点总结篇(一)

    JVM(Java Virtual Machine):源文件->编译器->字节码文件->解释器->程序: JDK:Java Development Kit,Java开发工具包: ...

  2. Golang修改json文件的两种方法

    第三方包 go get -u github.com/tidwall/sjson bytes, _ := ioutil.ReadFile(jsonFile) value1, _ := sjson.Set ...

  3. John Lemon's Haunted Jaunt(鬼屋游戏笔记)

    1.使用Unity  2019.2.3 2.角色移动的控制脚本 3.后期处理组件PostProcessLayer  (类似给相机加上了一层滤镜) 4.制作简单的怪物AI系统,使用 NAvMeshAge ...

  4. ubuntu安装texlive2019

    1.下载texlive2019的iso文件,清华镜像地址:https://mirrors.tuna.tsinghua.edu.cn/CTAN/systems/texlive/Images/texliv ...

  5. JavaScript之原型、函数、实例

    JavaScript 函数语法 函数就是包裹在花括号中的代码块,前面使用了关键词 function: function functionname() {    // 执行代码 } 当调用该函数时,会执 ...

  6. 【DATAGUARD】物理dg配置客户端无缝切换 (八.4)--ora-16652 和 ora-16603错误

    [DATAGUARD]物理dg配置客户端无缝切换 (八.4)--ora-16652 和 ora-16603错误 一.1  BLOG文档结构图       一.2  前言部分   一.2.1  导读 各 ...

  7. Shell 行遍历命令行的输出结果

      对于命令行输出的结果,如果要遍历,一般都是用for循环遍历,具体语法为: for line in `ls` do dosomethingdone   此时对于ls这类语句的输出结果,在遍历的时候会 ...

  8. windows 任务计划

    我的需求是每天定时访问网站的某一个控制器去刷新库存 流程如下(我自己的理解) 进入任务计划页面 上图指定的bat文件内容就是访问指定的网站路径 dingshi.bat文件内容如下(这个是网上找的,可能 ...

  9. 实验3 SQL注入原理-万能密码注入

    实验目的 (1)理解[万能密码]的原理 (2)学习[万能密码]的使用 实验原理 一.访问目标网站 1.选择一个存在漏洞的论坛 http://192.168.1.3:8009 进入 2.输入用户名[ad ...

  10. Codeforces F. Vus the Cossack and Numbers(贪心)

    题目描述: D. Vus the Cossack and Numbers Vus the Cossack has nn real numbers aiai. It is known that the ...