杭电 1874 错误代码还没改

import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;

public class Main{
	
	static boolean flag=true; 
	public static void main(String[] args) {
		
		Scanner in = new Scanner(System.in);
		int n=in.nextInt();
		int m=in.nextInt();
		int graph[][] = new int[n][n];
		int dis[] = new int[n];
		int count[] = new int[n];
		boolean used[] = new boolean[n];
		
		for(int i=0;i<n;i++) {//原来的话graph数组没有初始化，所以对后来spfa算法里if的判断条件造成了影响
			for(int j=0;j<n;j++) {
				graph[i][j] = Integer.MAX_VALUE;
			}
		}
		
		int start=in.nextInt();
		int end = in.nextInt();
		
		for(int i=0;i<n;i++) {
			
			int r=in.nextInt();
			int c=in.nextInt();
			graph[r-1][c-1] = in.nextInt();
			
		}
		
		for(int i=0;i<n;i++) {
			dis[i] = i==start?0:Integer.MAX_VALUE;
		}
		
		spfa(dis,graph,used,count,end);
	}
	
	public static void spfa(int dis[],int graph[][],boolean used[],int count[],int end) {
		
		Queue<Integer> q= new LinkedList<Integer>();
		q.add(0);
		used[0] = true;
		count[0]++;
		int tempt=0;
		while(!q.isEmpty()) {
			
			//System.out.println(100);
			int head = q.peek();//原来q.poll()及Used[head]=false是在这里的，给挪到后面去了
			for(int i=0;i<dis.length;i++) {
				if(i!=head&&graph[head][i]!=Integer.MAX_VALUE) {
						dis[i] = dis[i]>dis[head]+graph[head][i]?dis[head]+graph[head][i]:dis[i];
						
						if(!used[i]) {//原来上面的dis[i]=……是在if条件里面，逻辑好像有些问题
							used[i] = true;
							q.add(i);
							count[i]++;
							tempt=i;
						}
				}
			}
			if(count[tempt]>dis.length) {
				flag = false;
				break;
			}
			q.poll();
			used[head] = false;
		}
//		for(int k=1;k<dis.length;k++) {
//			
//			System.out.println(dis[k]);
//		}
		if(flag) {
			
			System.out.println(dis[end]);
		}else {
			System.out.println(-1);
		}
		
		
	}
}