拓扑排序+最短路径（无环加权有向图最短路径算法）

来源：互联网发布：淘宝服务商入驻条件编辑：程序博客网时间：2024/05/19 19:15

特点：
   1、线性时间内解决单点最短路径问题
   2、能够处理负权边问题
   3、能够找出最长路径
不足：因为是基于拓扑排序的，所以不能解决带环的问题

import java.util.ArrayList;import java.util.Scanner;import java.util.Stack;import Graph.HasCycle;public class TopDij {static boolean[]visit;static boolean[]onStack;static Stack<Integer> stack;static int n, m;static boolean hasCycle = false;static int[]dis;static int INF = 99999999;static ArrayList<EdgeS> []adj;public static void main(String[] args) {Scanner in = new Scanner(System.in);n = in.nextInt();m = in.nextInt();visit = new boolean[n+1];adj = new ArrayList[n+1];stack = new Stack<>();dis = new int[n+1];onStack = new boolean[n+1];for(int i = 1; i <= n; i++ ) {adj[i] = new ArrayList<>();}for(int i = 0; i < m; i++ ) {int from = in.nextInt();int to = in.nextInt();int w = in.nextInt();adj[from].add(new EdgeS(from, to, w));}bfs(1);//while(!stack.isEmpty()) {//System.out.println(stack.pop() + " ");//}if(!hasCycle) {shortPath(1);for(int i = 1; i <= n; i++ ) {System.out.println(dis[i] + " ");}}else {System.out.println("hasCycle");}}public static void shortPath(int s) {for(int i = 1; i <= n; i++ ) {dis[i] = 99999999;}dis[s] = 0;while(!stack.isEmpty()) {int cur = stack.pop();for(EdgeS e: adj[cur]) {if(dis[e.to] > dis[cur] + e.w) {dis[e.to] = dis[cur] + e.w;}}}}public static void bfs(int cur) {// 进行拓扑排序的同时检查是否含有环 有环的话就退出visit[cur] = true;onStack[cur] = true;for(EdgeS e:adj[cur]) {if(!visit[e.to]) {bfs(e.to);}else if(onStack[e.to]){hasCycle = true;return;}}onStack[cur] = false;stack.push(cur);//记录拓扑排序结果 、逆后序}}class EdgeS{int from, to, w;public EdgeS(int f, int t, int w) {from = f;to = t;this.w = w;}}

阅读全文

0 0