Submission #19264

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
19264	2016-02-23T14:05:41 Z	kriii	악수 (kriii4_D)	C++14	100 / 100	1238 ms	6600 KB

D

#include <stdio.h>

const long long mod = 1000000007;
long long inv[800],comb[800][800],end[41][800],all[41][800];

int main()
{
	int n,m; scanf ("%d",&n);
	comb[0][0] = comb[1][0] = comb[1][1] = inv[1] = 1;
	for (int i=2;i<800;i++){
		comb[i][0] = comb[i][i] = 1;
		for (int j=1;j<i;j++) comb[i][j] = (comb[i-1][j-1] + comb[i-1][j]) % mod;
		inv[i] = (mod - mod / i) * inv[mod % i] % mod;
	}

	end[1][0] = all[1][0] = 1;
	for (int v=2;v<=n;v++){
		int l = v * (v - 1) / 2;
		for (int e=v-1;e<=l;e++){
			for (int i=0;i<v-1;i++) for (int j=0;j<e;j++){
				long long add = comb[v-1][i] * comb[e-1][j] % mod;
				add = add * all[i+1][j] % mod;
				add = add * all[v-i-1][e-j-1] % mod;
				add = add * (i + 1) * (v - i - 1) % mod;
				end[v][e] += add;
			}
			end[v][e] %= mod;
			all[v][e] = (end[v][e] + (l - e + 1) * all[v][e-1]) % mod;
		}
	}

	long long coeff = 1, ans = 0;
	m = n * (n - 1) / 2;
	for (int i=1;i<=m;i++){
		coeff = coeff * inv[m-i+1] % mod;
		ans = (ans + end[n][i] * coeff % mod * i) % mod;
	}
	printf ("%lld\n",ans);

	return 0;
}

Subtask #1

5.0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	0 ms	6600 KB	Output is correct
2	Correct	0 ms	6600 KB	Output is correct
3	Correct	2 ms	6600 KB	Output is correct
4	Correct	0 ms	6600 KB	Output is correct
5	Correct	2 ms	6600 KB	Output is correct

Subtask #2

95.0 / 95.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	0 ms	6600 KB	Output is correct
2	Correct	0 ms	6600 KB	Output is correct
3	Correct	2 ms	6600 KB	Output is correct
4	Correct	0 ms	6600 KB	Output is correct
5	Correct	0 ms	6600 KB	Output is correct
6	Correct	0 ms	6600 KB	Output is correct
7	Correct	3 ms	6600 KB	Output is correct
8	Correct	3 ms	6600 KB	Output is correct
9	Correct	4 ms	6600 KB	Output is correct
10	Correct	5 ms	6600 KB	Output is correct
11	Correct	7 ms	6600 KB	Output is correct
12	Correct	6 ms	6600 KB	Output is correct
13	Correct	12 ms	6600 KB	Output is correct
14	Correct	16 ms	6600 KB	Output is correct
15	Correct	17 ms	6600 KB	Output is correct
16	Correct	27 ms	6600 KB	Output is correct
17	Correct	36 ms	6600 KB	Output is correct
18	Correct	46 ms	6600 KB	Output is correct
19	Correct	59 ms	6600 KB	Output is correct
20	Correct	75 ms	6600 KB	Output is correct
21	Correct	94 ms	6600 KB	Output is correct
22	Correct	117 ms	6600 KB	Output is correct
23	Correct	143 ms	6600 KB	Output is correct
24	Correct	180 ms	6600 KB	Output is correct
25	Correct	221 ms	6600 KB	Output is correct
26	Correct	268 ms	6600 KB	Output is correct
27	Correct	325 ms	6600 KB	Output is correct
28	Correct	386 ms	6600 KB	Output is correct
29	Correct	466 ms	6600 KB	Output is correct
30	Correct	552 ms	6600 KB	Output is correct
31	Correct	655 ms	6600 KB	Output is correct
32	Correct	772 ms	6600 KB	Output is correct
33	Correct	914 ms	6600 KB	Output is correct
34	Correct	1058 ms	6600 KB	Output is correct
35	Correct	1238 ms	6600 KB	Output is correct