HDU 5036 Explosion（北京网络赛E题）

HDU 5036 Explosion

#include <cstdio>
#include <cstring>
#include <bitset>
using namespace std;

const int N = 1005;
int t, n;
bitset<N> bs
;

int main() {
int cas = 0;
scanf("%d", &t);
while (t--) {
scanf("%d", &n);
for (int i = 0; i < n; i++) {
bs[i].reset();
bs[i][i] = true;
}
int num, v;
for (int i = 0; i < n; i++) {
scanf("%d", &num);
while (num--) {
scanf("%d", &v); v--;
bs[i][v] = true;
}
}
for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
if (bs[j][i])
bs[j] |= bs[i];
double ans = 0;
for (int i = 0; i < n; i++) {
int cnt = 0;
for (int j = 0; j < n; j++)
if (bs[j][i]) cnt++;
ans += 1.0 / cnt;
}
printf("Case #%d: %.5lf\n", ++cas, ans);
}
return 0;
}