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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
#213574#2715. 8.4t4jsxheng100790ms138604kbC++111.3kb2024-11-12 21:04:472024-11-12 23:45:13

answer

#include<bits/stdc++.h>
#define int long long
using namespace std;
namespace IO{
	template<typename T> inline void read(T &x){
		bool f=1;x=0;char ch=getchar();
		while(ch<'0'||ch>'9'){if(ch=='-')f=0;ch=getchar();}
		while(ch>='0'&&ch<='9')x=(x<<1)+(x<<3)+(ch&15),ch=getchar();
		x=f?x:-x;
	}
	template<typename T> inline void write(T x){
		if(x<0) putchar('-'),x=-x;
	   	if(x>9) write(x/10);
	   	putchar(('0'+x%10));
	}
	template <typename T,typename ...Args> inline void read(T &x,Args &...args){read(x);read(args...);}
	template<typename T> inline void write(T x,char c){write(x),putchar(c);}
}
using namespace IO;
const int N=5005,mod=1e9+7;
int n,f[N][N],siz[N],C[N][N];
vector<int>e[N];
void dfs(int u,int fa){
	f[u][1]=1,siz[u]=1;
	for(int v:e[u]){
		if(v!=fa){
			dfs(v,u);
			for(int i=siz[u];i;--i){
				for(int j=siz[v];j;j--)f[u][i+j]=(f[u][i+j]+f[u][i]*f[v][j]%mod*C[i+j-1][j])%mod;
				f[u][i]=f[u][i]*f[v][0]%mod;
			}
			siz[u]+=siz[v];
		}
	}
	for(int i=siz[u];~i;--i)f[u][i]=(f[u][i]+f[u][i+1])%mod;
}
signed main(){
	read(n);
	for(int i=1,u,v;i<n;++i){
		read(u,v);
		e[u].push_back(v),e[v].push_back(u);
	}
	for(int i=0;i<=n;++i){
		C[i][0]=1;
		for(int j=1;j<=i;++j)C[i][j]=(C[i-1][j-1]+C[i-1][j])%mod;
	}
	dfs(1,1);
	write(f[1][0]);
	return 0;
}

详细

小提示:点击横条可展开更详细的信息

Test #1:

score: 10
Accepted
time: 0ms
memory: 1380kb

input:

10
1 2
1 3
3 4
3 5
3 6
3 7
1 8
5 9
5 10

output:

227506

result:

ok found '227506.00000', expected '227506.00000', error '0.00000'

Test #2:

score: 10
Accepted
time: 0ms
memory: 1376kb

input:

10
1 2
1 3
3 4
4 5
5 6
4 7
5 8
8 9
8 10

output:

70140

result:

ok found '70140.00000', expected '70140.00000', error '0.00000'

Test #3:

score: 10
Accepted
time: 2ms
memory: 2152kb

input:

100
1 2
1 3
1 4
3 5
5 6
4 7
7 8
8 9
8 10
3 11
7 12
1 13
5 14
8 15
10 16
7 17
1 18
6 19
10 20
15 21
7...

output:

875072841

result:

ok found '875072841.00000', expected '875072841.00000', error '0.00000'

Test #4:

score: 10
Accepted
time: 2ms
memory: 2156kb

input:

100
1 2
2 3
3 4
4 5
4 6
6 7
5 8
8 9
8 10
1 11
6 12
4 13
9 14
13 15
7 16
3 17
15 18
17 19
9 20
8 21
4...

output:

706867541

result:

ok found '706867541.00000', expected '706867541.00000', error '0.00000'

Test #5:

score: 10
Accepted
time: 0ms
memory: 2156kb

input:

100
1 2
2 3
3 4
2 5
2 6
5 7
2 8
4 9
7 10
5 11
11 12
6 13
8 14
13 15
5 16
11 17
16 18
11 19
7 20
19 2...

output:

515055734

result:

ok found '515055734.00000', expected '515055734.00000', error '0.00000'

Test #6:

score: 10
Accepted
time: 0ms
memory: 6332kb

input:

500
1 2
1 3
3 4
3 5
5 6
1 7
3 8
8 9
4 10
6 11
7 12
2 13
11 14
8 15
7 16
9 17
2 18
3 19
15 20
2 21
20...

output:

28964814

result:

ok found '28964814.00000', expected '28964814.00000', error '0.00000'

Test #7:

score: 10
Accepted
time: 0ms
memory: 6328kb

input:

500
1 2
1 3
1 4
2 5
5 6
5 7
4 8
8 9
1 10
4 11
8 12
6 13
13 14
13 15
12 16
1 17
10 18
13 19
1 20
1 21...

output:

900482908

result:

ok found '900482908.00000', expected '900482908.00000', error '0.00000'

Test #8:

score: 10
Accepted
time: 261ms
memory: 138544kb

input:

5000
1 2
1 3
1 4
3 5
3 6
5 7
4 8
4 9
1 10
5 11
6 12
10 13
12 14
14 15
12 16
8 17
14 18
9 19
8 20
20 ...

output:

255910011

result:

ok found '255910011.00000', expected '255910011.00000', error '0.00000'

Test #9:

score: 10
Accepted
time: 261ms
memory: 138604kb

input:

5000
1 2
1 3
1 4
2 5
1 6
5 7
2 8
5 9
4 10
9 11
10 12
8 13
7 14
13 15
12 16
5 17
9 18
8 19
3 20
4 21
...

output:

506490313

result:

ok found '506490313.00000', expected '506490313.00000', error '0.00000'

Test #10:

score: 10
Accepted
time: 264ms
memory: 138532kb

input:

5000
1 2
1 3
1 4
4 5
4 6
3 7
2 8
8 9
6 10
9 11
3 12
3 13
7 14
13 15
4 16
10 17
9 18
10 19
5 20
17 21...

output:

738067707

result:

ok found '738067707.00000', expected '738067707.00000', error '0.00000'