floyd

#include<bits/stdc++.h>
using namespace std;
const int N = 202, INF = 0x3f3f3f3f;
int n, m, q;
int g[N][N];

void floyd()
{
    for(int k = 1; k <= n; k ++ )
        for(int i = 1; i <= n; i ++ )
            for(int j = 1; j <= n; j ++ )
                g[i][j] = min(g[i][j], g[i][k] + g[k][j]);
}

int main()
{
    cin >> n >> m >> q;
    for(int i = 0; i <= n; i ++ )
        for(int j = 0; j <= n; j ++ )
            if(i == j) g[i][j] = 0;
            else g[i][j] = INF;

    while(m -- )
    {
        int f, t, l;
        cin >> f >> t >> l;
        g[f][t] = min(g[f][t], l);
    }

    floyd();

    while(q -- )
    {
        int f, t;
        cin >> f >> t;
        if(g[f][t] > INF / 2) puts("impossible");
        else cout << g[f][t] << endl;
    }

    return 0;
}

 

posted @ 2022-09-01 09:07  ginkgozyf  阅读(162)  评论(0)    收藏  举报