B

http://acm.sdut.edu.cn:8080/vjudge/contest/view.action?cid=76#problem/B

#include <stdio.h>
#include <string.h>
#include <math.h>
#define INF 1<<20
int map[201][201];

void floyd(int n)
{
    int i,j,k;
    for(k = 0;k<=n;k++)
    {
        for(i = 0;i<=n;i++)
        {
            for(j = 0;j<=n;j++)
            {
                if(map[i][j]>map[i][k] + map[k][j])
                {
                    map[i][j] = map[i][k] + map[k][j];
                }
            }
        }
    }
}
int n,m,s,t;
int main()
{
    int i,j;
    int u,v,w;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        for(i = 0;i<=n;i++)
        {
            for(j = 0;j<=n;j++)
            {
                if(i == j)
                map[i][j] = 0;
                else
                map[i][j] = INF;
            }
        }
        for(i = 1;i<=m;i++)
        {
            scanf("%d%d%d",&u,&v,&w);
            if(map[v][u]>w)
            {
                map[u][v] = map[v][u] = w;
            }
        }
        floyd(n);
        scanf("%d%d",&s,&t);
        if(map[s][t]>=INF)
        printf("-1
");
        else
        printf("%d
",map[s][t]);
    }
    return 0;
}