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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
#691648#6137. Sub-cycle GraphA_Quark#AC ✓136ms5004kbC++201.3kb2024-10-31 12:27:092024-10-31 12:27:10

Judging History

你现在查看的是最新测评结果

  • [2024-10-31 12:27:10]
  • 评测
  • 测评结果:AC
  • 用时:136ms
  • 内存:5004kb
  • [2024-10-31 12:27:09]
  • 提交

answer

#include<bits/stdc++.h>
#define i64 long long
using namespace std;
inline i64 rd()
{
	i64 num=0;char ch=getchar();bool op=0;
	for(;!isdigit(ch);ch=getchar())if(ch=='-')op=1;
	for(;isdigit(ch);ch=getchar())num=num*10+(ch-'0');
	return op?-num:num;
}
const int mod=1000000007;
inline int Mod(int x){return x>=mod?x-mod:x;}
inline void Add(int&x,int v){x+=v;if(x>=mod)x-=mod;}
inline i64 qpow(i64 val,int p=mod-2)
{
	i64 res=1;
	while(p)
	{
		if(p&1)res=res*val%mod;
		val=val*val%mod;p>>=1;
	}
	return res;
}
const int N=1e5+10;
int fac[N],ifac[N];
int ipw[N];
inline void predone(int n=1e5+5)
{
	int ibase=qpow(2);
	ipw[0]=1;
	for(int i=1;i<=n;i++)ipw[i]=1ll*ipw[i-1]*ibase%mod;
	fac[0]=1;
	for(int i=1;i<=n;i++)fac[i]=1ll*fac[i-1]*i%mod;
	ifac[n]=qpow(fac[n]);
	for(int i=n;i>=1;i--)ifac[i-1]=1ll*ifac[i]*i%mod;
}
inline int C(int n,int m){return n<m||m<0?0:1ll*fac[n]*ifac[m]%mod*ifac[n-m]%mod;}

inline void work()
{
	int n=rd();i64 m=rd();
	if(n< m){printf("0\n");return;}
	if(n==m){printf("%lld\n",1ll*fac[n-1]*qpow(2)%mod);return;}
	if(0==m){printf("1\n");return;}
	m=n-m;int Ans=0;
	for(int i=1;i<=m;i++)
		Add(Ans,1ll*C(n,m-i)*fac[n-(m-i)]%mod*C(n-(m-i)-i-1,i-1)%mod*ipw[i]%mod*ifac[i]%mod);
	printf("%d\n",Ans);
}
int main()
{
	predone();
	for(int test=rd();test;test--)work();
	return 0;
}

詳細信息

Test #1:

score: 100
Accepted
time: 2ms
memory: 5004kb

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: 136ms
memory: 4948kb

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