测试样例补充：卡码网-47. 参加科学大会 #2992

#include<iostream>
#include<vector>
#include<string.h>
#include<queue>
#include<climits>
using namespace std;

int edges[505][505];
bool visited[505];

int main()
{
    int n, m;
    cin >> n >>  m;
    memset(edges, 0, sizeof(edges));
    memset(visited, false, sizeof(visited));
    int s, t, val;
    while(m--){
        scanf("%d%d%d", &s, &t, &val);
        edges[s][t] = val;
    }

    vector<int>dist(n+1, INT_MAX);
    queue<int>q;
    q.push(1);
    dist[1] = 0;
    while(!q.empty()){
        int cur = q.front();    q.pop();
        visited[cur] = true;
        for(int t=1; t<=n; t++){
            if(edges[cur][t]==0)    continue;
            dist[t] = min(dist[t], dist[cur]+edges[cur][t]);
            if(!visited[t])  q.push(t);
        }
    }
    // for(int i=1; i<n; i++)
    //     if(edges[i][n]!=0){
    //         dist[n] = min(dist[n], dist[i]+edges[i][n]);
    //     }
    if(dist[n] == INT_MAX)  cout << -1;
    else    cout << dist[n];
}

4 4
1 2 2000
1 3 1
3 2 1
2 4 1