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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
#144221#6137. Sub-cycle Graphsihan_88WA 98ms3976kbC++14996b2023-08-21 15:57:442023-08-21 15:57:47

Judging History

你现在查看的是最新测评结果

  • [2023-08-21 15:57:47]
  • 评测
  • 测评结果:WA
  • 用时:98ms
  • 内存:3976kb
  • [2023-08-21 15:57:44]
  • 提交

answer

#include<cstdio>
typedef long long ll;
const int MOD=int(1e9)+7;
const int INV2=(MOD+1)>>1;
inline ll ksm(ll b,int p)
{
	ll res=1;
	for(;p;p>>=1,b=b*b%MOD) if(p&1) (res*=b)%=MOD;
	return res;
}
const int N=100010;
ll fact[N],fact_inv[N],P[N];
inline ll C(int n,int m)
{
	if(n<0||m<0||n<m) return 0;
	return fact[n]*fact_inv[m]%MOD*fact_inv[n-m]%MOD;
}
inline ll F(int n,int m)
{
	//a_i\ge2 \sum_{a_i}=n
	if(!m) return n==0;
	return C(n-m-1,m-1);
}
int main()
{
	fact[0]=P[0]=1;
	for(int i=1;i<N;++i) fact[i]=fact[i-1]*i%MOD,P[i]=P[i-1]*INV2%MOD;
	fact_inv[N-1]=ksm(fact[N-1],MOD-2);
	for(int i=N-2;i>=0;--i) fact_inv[i]=fact_inv[i+1]*(i+1)%MOD;
	int T,n;
	ll m;
	scanf("%d",&T);
	while(T--)
	{
		scanf("%d%lld",&n,&m);
		if(m>n) puts("0");
		else if(m==n) printf("%lld\n",fact[n-1]);
		else
		{
			ll sum=0;
			for(int i=0;i<=n-m;++i) sum=(sum+C(n-m,i)*P[i]%MOD*F(m+i,i))%MOD;
			printf("%lld\n",sum*fact[n]%MOD*fact_inv[n-m]%MOD);
		}
	}
	return 0;
}

详细

Test #1:

score: 100
Accepted
time: 0ms
memory: 3876kb

input:

3
4 2
4 3
5 3

output:

15
12
90

result:

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

Test #2:

score: -100
Wrong Answer
time: 98ms
memory: 3976kb

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
2
1
6
15
12
6
1
10
45
90
60
24
1
15
105
375
630
360
120
1
21
210
1155
3465
5040
2520
720
1
28
378
2940
13545
35280
45360
20160
5040
1
36
630
6552
42525
170100
393120
453600
181440
40320
1
45
990
13230
114345
643545
2286900
4762800
4989600
1814400
362880
1
55
1485
24750
273735
2047815
10239075
...

result:

wrong answer 4th numbers differ - expected: '1', found: '2'