C++ 代码

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cstdio>
using namespace std;
const int N = 210, INF = 0x3f3f3f3f;
int dist[N][N];
int n,m,k;
void floyd()
{
    for(int k = 1; k <= n ; k ++ )
      for(int i = 1; i <= n ;i ++ )
        for(int j = 1; j <= n ; j ++ )
          dist[i][j] = min(dist[i][j],dist[i][k] + dist[k][j]);
}
int main()
{
    memset(dist,INF,sizeof dist);
    cin >> n >> m >> k;
    for(int i = 0 ; i < m ; i ++ )
    {
        int a,b,c;
        scanf("%d%d%d",&a,&b,&c);
        dist[a][b] = min(dist[a][b], c);
    }
    for(int i = 1 ; i <= n ; i++ ) dist[i][i] = 0;
    floyd();
    while(k--)
    {
        int a,b;
        scanf("%d%d",&a,&b);
        if(dist[a][b]>=INF/2) puts("impossible");
        else cout << dist[a][b] << endl;
    }
    return 0;
}