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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
#105251#6137. Sub-cycle GraphSorting#WA 187ms5624kbC++1.2kb2023-05-13 19:59:132023-05-13 19:59:14

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.
  • [2023-05-13 19:59:14]
  • 评测
  • 测评结果:WA
  • 用时:187ms
  • 内存:5624kb
  • [2023-05-13 19:59:13]
  • 提交

answer

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll mod=1e9+7;
const int iu=1e5;
ll f[100001],inf[100001];
ll ph[100001];
ll pw(ll x,ll y){
	if(y==0) return 1;
	if(y%2) return x*pw(x,y-1)%mod;
	ll res=pw(x,y/2);
	return res*res%mod;
}
ll C(int x,int y){
	if(y<0 || y>x) return 0;
	return f[x]*inf[y]%mod*inf[x-y]%mod;
}
ll inv(int d){
	return f[d-1]*inf[d]%mod;
}
ll n,m;
void solve(){
	cin >> n >> m;
	if(m>n){
		cout << "0\n";
		return;
	}
	if(m==n){
		cout << f[n-1] << '\n';
		return;
	}
	ll ans=0;
	for(int k=0; k<n-m ;k++){
		ll w1=C(n,k);
		ll w2=f[n-k-1];//arrange into cycle
		ll rep=inv(m)*(n-k)%mod*C(m,n-k-m)%mod;//arrange m*1 and (n-k-m)*0 in a circle so that no two 0 adjacent
		ll cur=w1*w2%mod*rep%mod*ph[n-k-m]%mod*inf[n-k-m-1]%mod;
		ans=(ans+cur)%mod;
		//cout << n << ' ' << k << ' ' << w1 << ' ' << w2 << ' ' << rep << ' ' << cur << endl;
	}
	cout << ans << '\n';
}
int main(){
	ios::sync_with_stdio(false);cin.tie(0);
	f[0]=1;
	for(int i=1; i<=iu ;i++) f[i]=f[i-1]*i%mod;
	inf[iu]=pw(f[iu],mod-2);
	for(int i=iu; i>=1 ;i--) inf[i-1]=inf[i]*i%mod;
	ph[0]=1;
	for(int i=1; i<=iu ;i++) ph[i]=ph[i-1]*(mod+1)/2%mod;
	int t;cin >> t;
	while(t--) solve();
}

详细

Test #1:

score: 100
Accepted
time: 5ms
memory: 5604kb

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: 187ms
memory: 5624kb

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:

0
3
3
2
0
6
15
12
6
0
10
45
90
60
24
0
15
105
375
630
360
120
0
21
210
1155
3465
5040
2520
720
0
28
378
2940
13545
35280
45360
20160
5040
0
36
630
6552
42525
170100
393120
453600
181440
40320
0
45
990
13230
114345
643545
2286900
4762800
4989600
1814400
362880
0
55
1485
24750
273735
2047815
10239075
...

result:

wrong answer 1st numbers differ - expected: '1', found: '0'