poj 2139 Six Degrees of Cowvin Bacon , floyd

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题意：给定牛的关系图，求其中一头牛与其他牛关系路程之和sum最小，然后输出 sum*100/(n-1)

floyd求任意两点间的最短路程

注意： inf不能太大，因为 f[i][k] + f[k][j]  做加法时可能会溢出！

#include <cstdio>
#include <cstring>

const int maxn = 300 + 5;
const int inf = 1<<29;
int n, m;
int f[maxn][maxn];
int a[maxn];

void floyd()
{
    int i, j, k;
    for(k=1; k<=n; ++k)
        for(i=1; i<=n; ++i)
            for(j=1; j<=n; ++j) {
                if(f[i][j]> f[i][k] + f[k][j])
                    f[i][j] = f[i][k] + f[k][j];
            }
}
int main()
{
    int i, j, k, ans, ret;
    while(~scanf("%d%d",&n, &m)) {
        for(i=0; i<=n; ++i) {
            for(j=0; j<=n; ++j) f[i][j] = inf;
            f[i][i] = 0;
        }
        while(m--) {
            scanf("%d", &k);
            for(i=0; i<k; ++i) {
                scanf("%d", &a[i]);
                for(j=0; j<i; ++j)
                    f[a[i]][a[j]] = f[a[j]][a[i]] = 1;
            }
        }
        floyd();

        ans = inf;
        for(i=1; i<=n; ++i) {
            ret = 0;
            for(j=1; j<=n; ++j)
                ret += f[i][j];
            if(ans > ret) ans = ret;
        }
        printf("%d\n", ans*100/(n-1));
    }
    return 0;
}

poj 2139 Six Degrees of Cowvin Bacon , floyd