warshall-floyd算法：POJ No 2139 Six Degress of Cowvin Bacon（任意两点最短路径））

#include <iostream>
#include <algorithm>
#include <iomanip>
using namespace std;

const int maxn = 300 + 24;
const int INF = 99999999;
int N, M;           // N个牛 ，M组电影
//不存在的时候等于无穷大 或者
//d[i][i] = 0
int d[maxn][maxn];  //d[u][v]表示边e=(u,v)的权值
int x[maxn];

void warshall_floyd();
void init();

void init()
{
for (int i = 0; i < N; i++) {
for (int j = 0; j < N; j++) {
if (i == j) {
d[i][j] = 0;
} else {
d[i][j] = INF;
}
}
}
}

void warshall_floyd()
{
//经过顶点和不经过顶点的情况
for (int k = 0; k < N; k++) {
for (int i = 0; i < N; i++) {
for (int j = 0; j < N; j++) {
d[i][j] = min(d[i][j], d[i][k] + d[k][j]);
}
}
}
}

void solve()
{
int n;
scanf("%d%d", &N, &M);
init();

while (M--)
{
scanf("%d", &n);
for (int i = 0; i < n; i++) {
scanf("%d", &x[i]);
--x[i];
}

for (int i = 0; i < n; i++)
{
for (int j = i + 1; j < n; j++) {
d[x[i]][x[j]] = d[x[j]][x[i]] = 1;
}
}
}
warshall_floyd();
int ans = INF;
for (int i = 0; i < N; i++)
{
int sum = 0;
for (int j = 0; j < N; j++) {
sum += d[i][j];
}
ans = min(ans, sum);
}

printf("%d\n", 100 * ans / (N - 1));

}

int main()
{
solve();

return 0;

}