QOJ.ac

QOJ

ID题目提交者结果用时内存语言文件大小提交时间测评时间
#94466#6137. Sub-cycle GraphxuzhihaodedieAC ✓345ms8772kbC++141.4kb2023-04-06 10:51:222023-04-06 10:51:26

Judging History

你现在查看的是最新测评结果

  • [2023-08-10 23:21:45]
  • System Update: QOJ starts to keep a history of the judgings of all the submissions.
  • [2023-04-06 10:51:26]
  • 评测
  • 测评结果:AC
  • 用时:345ms
  • 内存:8772kb
  • [2023-04-06 10:51:22]
  • 提交

answer

// Problem: E. Living Sequence
// Contest: Codeforces - Codeforces Round 863 (Div. 3)
// URL: https://codeforces.com/contest/1811/problem/E
// Memory Limit: 256 MB
// Time Limit: 1000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int mod=1e9+7;
const int N=1e5+10;
int fact[2*N],infact[2*N];
int pw[2*N];
int f[2*N];
int qpow(int a,int b) {
	if(b==0) return 1;
	if(b&1) return a*qpow(a,b-1)%mod;
	else {
		int mul=qpow(a,b/2)%mod;
		return mul*mul%mod;
	}
}
void init() {
	fact[0]=infact[0]=pw[0]=f[0]=1;
	for(int i=1;i<2*N;i++) {
		fact[i]=fact[i-1]*i%mod;
		infact[i]=qpow(fact[i],mod-2)%mod;
		pw[i]=pw[i-1]*2%mod;
	}
	for(int i=1;i<N;i++) {
		f[i]=f[i-1]*(2*i-1)%mod;
	}
}
int c(int n,int m) {
	if(n<m) return 0;
	if(n<0||m<0) return 0;
	return fact[n]*infact[n-m]%mod*infact[m]%mod;
}
void solve() {
	int n,m;
	cin>>n>>m;
	if(m>n) {
		cout<<0<<endl;
		return ;
	}
	if(m==0) {
		cout<<1<<endl;
		return ;
	}
	if(m==n) {
		if(n<=2) {
			cout<<0<<endl;
		} else {
			cout<<fact[n-1]*qpow(2,mod-2)%mod<<endl;
		}
		return ;
	}
	int ans=0;
	for(int t=0;t<=n-m;t++) {
		int res=c(n,t)*c(n-t,2*(n-m-t))%mod*c(m-1,n-m-t-1)%mod;
		int ret=f[n-m-t];
		ans=(ans+ret*res%mod*fact[max(0ll,2*m+t-n)]%mod)%mod;
	}
	cout<<ans<<endl;
}
signed main() {
	int T=1;
	init();
	cin>>T;
	while(T--) {
		solve();
	}
}

詳細信息

Test #1:

score: 100
Accepted
time: 58ms
memory: 8756kb

input:

3
4 2
4 3
5 3

output:

15
12
90

result:

ok 3 number(s): "15 12 90"

Test #2:

score: 0
Accepted
time: 345ms
memory: 8772kb

input:

17446
3 0
3 1
3 2
3 3
4 0
4 1
4 2
4 3
4 4
5 0
5 1
5 2
5 3
5 4
5 5
6 0
6 1
6 2
6 3
6 4
6 5
6 6
7 0
7 1
7 2
7 3
7 4
7 5
7 6
7 7
8 0
8 1
8 2
8 3
8 4
8 5
8 6
8 7
8 8
9 0
9 1
9 2
9 3
9 4
9 5
9 6
9 7
9 8
9 9
10 0
10 1
10 2
10 3
10 4
10 5
10 6
10 7
10 8
10 9
10 10
11 0
11 1
11 2
11 3
11 4
11 5
11 6
11 7
11...

output:

1
3
3
1
1
6
15
12
3
1
10
45
90
60
12
1
15
105
375
630
360
60
1
21
210
1155
3465
5040
2520
360
1
28
378
2940
13545
35280
45360
20160
2520
1
36
630
6552
42525
170100
393120
453600
181440
20160
1
45
990
13230
114345
643545
2286900
4762800
4989600
1814400
181440
1
55
1485
24750
273735
2047815
10239075
3...

result:

ok 17446 numbers