zoj1221_Risk（多源点最短路）

多源点最短路，floyd

#include<iostream>
#include<vector>
#include<cstdio>
using namespace std;

int map[25][25];

void floyd()
{
    for (int k = 1; k <= 20; k++)
        for (int i = 1; i <= 20; i++)
            for (int j = 1; j <= 20; j++)
            {
                if (map[i][j] > map[i][k] + map[k][j])
                    map[i][j] = map[i][k] + map[k][j];
            }
}

int main()
{
    int t = 1;
    int n;
    while (~scanf("%d",&n))
    {
        for (int i = 1; i <= 20; i++)
            for (int j = 1; j <= 20; j++)
                map[i][j] = 999999;
        for (int i = 0; i < n; i++)
        {
            int a;
            scanf("%d", &a);
            map[1][a] = 1;
            map[a][1] = 1;
        }
        for (int i = 2; i < 20; i++)
        {
            int sum;
            scanf("%d", &sum);
            for (int j = 0; j < sum; j++)
            {
                int a;
                scanf("%d", &a);
                map[i][a] = 1;
                map[a][i] = 1;
            }
        }
        floyd();
        printf("Test Set #%d\n", t++);
        int m;
        scanf("%d", &m);
        for (int i = 0; i < m; i++)
        {
            int a, b;
            scanf("%d %d", &a, &b);
            printf("%d to %d: %d\n", a, b, map[a][b]);
        }
        printf("\n");
    }
    return 0;
}