Silver Cow Party java优先队列实现
2021/4/30 20:28:32
本文主要是介绍Silver Cow Party java优先队列实现,对大家解决编程问题具有一定的参考价值,需要的程序猿们随着小编来一起学习吧!
题目链接:Silver Cow Party
两次迪杰斯特拉即可。这次使用了优先队列。
import java.io.BufferedReader; import java.io.InputStreamReader; import java.util.*; public class Main { public static void main(String[] args) throws Exception { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); StringTokenizer st = new StringTokenizer(br.readLine()); int N = Integer.parseInt(st.nextToken()); int M = Integer.parseInt(st.nextToken()); int X = Integer.parseInt(st.nextToken()); ArrayList<Edge>[] roadOut = new ArrayList[N+1]; //ArrayList<Edge>[] roadBack = new ArrayList[N+1]; for(int i =1;i<=M;i++){ st = new StringTokenizer(br.readLine()); int start = Integer.parseInt(st.nextToken()); int end = Integer.parseInt(st.nextToken()); int weight = Integer.parseInt(st.nextToken()); if(roadOut[start] == null){ roadOut[start] = new ArrayList<Edge>(); } /* if(roadBack[end] == null){ roadBack[end] = new ArrayList<Edge>(); }*/ roadOut[start].add(new Edge(end,weight)); //roadBack[end].add(new Edge(start,weight)); } int[] visited = new int[N+1]; //go out search int[] goOutList = new int[N+1]; for(int m=1;m<=N;m++){ Arrays.fill(visited,100000000); visited[m]=0; PriorityQueue<Edge> pq = new PriorityQueue<Edge>(); Edge init = new Edge(m,0); pq.add(init); Edge pollEdge; int newDist; while(!pq.isEmpty()){ pollEdge = pq.poll(); for(Edge nextEdge:roadOut[pollEdge.end]){ newDist = visited[pollEdge.end]+nextEdge.weight; if(newDist<visited[nextEdge.end]){ visited[nextEdge.end] = newDist; pq.add(nextEdge); } } } goOutList[m] = visited[X]; } //return search int[] returnList = new int[N+1]; visited = new int[N+1]; for(int m = 1;m<=N;m++){ Arrays.fill(visited,100000000); visited[X]=0; PriorityQueue<Edge> pq = new PriorityQueue<Edge>(); Edge init = new Edge(X,0); pq.add(init); Edge pollEdge; int newDist; while(!pq.isEmpty()){ pollEdge = pq.poll(); for(Edge nextEdge:roadOut[pollEdge.end]){ newDist = visited[pollEdge.end]+nextEdge.weight; if(newDist<visited[nextEdge.end]){ visited[nextEdge.end] = newDist; pq.add(nextEdge); } } } returnList[m] = visited[m]; } int max=0; for(int m = 1;m<=N;m++){ max = Math.max(goOutList[m]+returnList[m],max); } System.out.println(max); } static class Edge implements Comparable<Edge>{ int end; int weight; public Edge(){ } public Edge(int end,int weight){ this.end = end; this.weight = weight; } @Override public int compareTo(Edge o) { return this.weight-o.weight; } } }
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