bzoj1430prufer序列

#include<iostream>#include<cstdio>#include<algorithm>using namespace std;const int mod = 9999991;int pow(int v, int t){long long ans = 1; long long value = v;while (t){if (t % 2)ans *= value,ans%=mod;value *= value; value %= mod; t >>= 1;}return ans;}int main(){int n;scanf("%d", &n);long long ans = pow(n, n - 2);for (int i = 1; i <= n - 1; i++)ans *= i, ans %= mod;printf("%lld\n", ans%mod);}

知道是prufer序列后不用分析一下就会做了。。。。