답안 #19926

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
19926	2016-02-25T07:20:02 Z	tonyjjw	악수 (kriii4_D)	C++14	100 / 100	669 ms	66740 KB

D

//*
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <time.h>
#include <stdlib.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <numeric>
#include <functional>
#define MOD 1000000007
#define MAX 0x3f3f3f3f
#define MAX2 0x3f3f3f3f3f3f3f3fll
#define ERR 1e-10
#define mp make_pair
#define all(x) (x).begin(), (x).end()
#pragma warning(disable:4996)
using namespace std;

typedef long long ll;
typedef long double ldb;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;

ll mul_inv(ll a, ll b=MOD)
{
	ll b0=b, t, q;
	ll x0=0, x1=1;
	if(b == 1) return 1;
	while(a > 1)
	{
		q=a/b;
		t=b, b=a%b, a=t;
		t=x0, x0=x1-q*x0, x1=t;
	}
	if(x1 < 0) x1+=b0;
	return x1;
}

ll ncr[2600][2600];
ll d[200][2600];
ll e[200][2600];
ll f[200][2600];
ll fac[2600];

int n;

ll npr(ll n, ll r)
{
	if(r > n) return 0;
	return fac[n]*mul_inv(fac[n-r])%MOD;
}

void addmod(ll &x, ll y)
{
	x+=y, x%=MOD;
}

int main()
{
	int i, j, k;
	cin>>n;
	if(n == 1) return !printf("0");
	for(i=0;i<2600;i++) for(j=0;j<=i;j++) ncr[i][j]=j==0||j==i?1:ncr[i-1][j-1]+ncr[i-1][j], ncr[i][j]%=MOD;
	fac[0]=1;
	for(i=1;i<2600;i++) fac[i]=fac[i-1]*i, fac[i]%=MOD;
	d[1][0]=1;
	e[1][0]=0;
	f[1][0]=1;
	d[2][0]=0;
	e[2][0]=1;
	f[2][0]=1;
	d[2][1]=1;
	e[2][1]=0;
	f[2][1]=1;
	for(i=3;i<=n;i++)
	{
		for(j=0;j<=ncr[i][2];j++)
		{
			f[i][j]=npr(ncr[i][2], j);
			ll xsum=0;
			for(int s=1;s<=i-1;s++)
			{
				ll sum=0;
				for(k=0;k<=j;k++)
				{
					addmod(sum, d[s][k]*f[i-s][j-k]%MOD*ncr[j][k]);
				}
				sum*=ncr[i-1][s-1], sum%=MOD;
				xsum+=sum, xsum%=MOD;
			}
			e[i][j]=xsum;
			d[i][j]=(f[i][j]-xsum)%MOD;
			if(d[i][j] < 0) d[i][j]+=MOD;
		}
	}
	ll ex=0;
	ll tot=fac[ncr[n][2]];
	for(j=1;j<=ncr[n][2];j++)
	{
		ex+=j*(d[n][j]*fac[ncr[n][2]-j]%MOD-d[n][j-1]*fac[ncr[n][2]-(j-1)]%MOD+MOD)%MOD;
		ex%=MOD;
	}
	ex*=mul_inv(tot);
	ex%=MOD;
	cout<<ex;
	return 0;
}
//*/

Subtask #1

5.0 / 5.0

#	결과	실행 시간	메모리	Grader output
1	Correct	0 ms	66740 KB	Output is correct
2	Correct	11 ms	66740 KB	Output is correct
3	Correct	4 ms	66740 KB	Output is correct
4	Correct	12 ms	66740 KB	Output is correct
5	Correct	8 ms	66740 KB	Output is correct

Subtask #2

95.0 / 95.0

#	결과	실행 시간	메모리	Grader output
1	Correct	4 ms	66740 KB	Output is correct
2	Correct	3 ms	66740 KB	Output is correct
3	Correct	10 ms	66740 KB	Output is correct
4	Correct	12 ms	66740 KB	Output is correct
5	Correct	0 ms	66740 KB	Output is correct
6	Correct	8 ms	66740 KB	Output is correct
7	Correct	20 ms	66740 KB	Output is correct
8	Correct	17 ms	66740 KB	Output is correct
9	Correct	13 ms	66740 KB	Output is correct
10	Correct	13 ms	66740 KB	Output is correct
11	Correct	19 ms	66740 KB	Output is correct
12	Correct	16 ms	66740 KB	Output is correct
13	Correct	25 ms	66740 KB	Output is correct
14	Correct	28 ms	66740 KB	Output is correct
15	Correct	26 ms	66740 KB	Output is correct
16	Correct	30 ms	66740 KB	Output is correct
17	Correct	30 ms	66740 KB	Output is correct
18	Correct	29 ms	66740 KB	Output is correct
19	Correct	51 ms	66740 KB	Output is correct
20	Correct	51 ms	66740 KB	Output is correct
21	Correct	70 ms	66740 KB	Output is correct
22	Correct	71 ms	66740 KB	Output is correct
23	Correct	97 ms	66740 KB	Output is correct
24	Correct	107 ms	66740 KB	Output is correct
25	Correct	133 ms	66740 KB	Output is correct
26	Correct	139 ms	66740 KB	Output is correct
27	Correct	188 ms	66740 KB	Output is correct
28	Correct	203 ms	66740 KB	Output is correct
29	Correct	255 ms	66740 KB	Output is correct
30	Correct	302 ms	66740 KB	Output is correct
31	Correct	356 ms	66740 KB	Output is correct
32	Correct	421 ms	66740 KB	Output is correct
33	Correct	492 ms	66740 KB	Output is correct
34	Correct	569 ms	66740 KB	Output is correct
35	Correct	669 ms	66740 KB	Output is correct