Submission #1816615


Source Code Expand

#include<bits/stdc++.h>
#define maxn 2010
#define mod 1000000007
using namespace std;
struct edge{
	int r,nxt;
}e[maxn<<1];
int head[maxn],esz,fac[maxn],dp[maxn][maxn][3],n;
void addedge(int u,int v){
	e[++esz].r=v;e[esz].nxt=head[u];head[u]=esz;
}
int dfs(int u){
	dp[u][0][0]=1;
	int sz=1,s;
	for(int t=head[u],v;t;t=e[t].nxt){
		s=dfs(v=e[t].r);
		for(int i=sz-1;i>=0;--i)
			for(int j=s-1;j>=0;--j){
				int A=(1ll*dp[v][j][0]+dp[v][j][1]+dp[v][j][2])%mod;
				dp[u][i+j+1][1]=(dp[u][i+j+1][1]+1ll*dp[u][i][0]*(2ll*dp[v][j][0]+dp[v][j][1]))%mod;
				dp[u][i+j+1][2]=(dp[u][i+j+1][2]+1ll*dp[u][i][1]*(dp[v][j][0]+1ll*dp[v][j][1]*(mod+1)/2%mod))%mod;
				if(j==0){
					dp[u][i][0]=1ll*dp[u][i][0]*A%mod;
					dp[u][i][1]=1ll*dp[u][i][1]*A%mod;
					dp[u][i][2]=1ll*dp[u][i][2]*A%mod;
				} else {
					dp[u][i+j][0]=(dp[u][i+j][0]+1ll*dp[u][i][0]*A)%mod;
					dp[u][i+j][1]=(dp[u][i+j][1]+1ll*dp[u][i][1]*A)%mod;
					dp[u][i+j][2]=(dp[u][i+j][2]+1ll*dp[u][i][2]*A)%mod;
				}
			}
			
		sz+=s;
	}
	return sz;
}
int main(){
	scanf("%d",&n),fac[0]=1;
	for(int i=1;i<=n;++i)
		fac[i]=1ll*fac[i-1]*i%mod;
	for(int i=2,x;i<=n;++i) 
		scanf("%d",&x),addedge(x,i);
	dfs(1);
	int ans=0;
	for(int i=0;i<n;++i)
		ans=(ans+1ll*(i&1?-1:1)*fac[n-i]*(1ll*dp[1][i][0]+dp[1][i][1]+dp[1][i][2])%mod+mod)%mod;
	printf("%d",ans);
} 

Submission Info

Submission Time
Task A - Awkward
User yfzcsc
Language C++14 (GCC 5.4.1)
Score 1000
Code Size 1364 Byte
Status AC
Exec Time 44 ms
Memory 47616 KB

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:38:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n),fac[0]=1;
                         ^
./Main.cpp:42:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&x),addedge(x,i);
                              ^

Judge Result

Set Name Sample All
Score / Max Score 0 / 0 1000 / 1000
Status
AC × 4
AC × 55
Set Name Test Cases
Sample a01, a02, a03, a04
All a01, a02, a03, a04, b05, b06, b07, b08, b09, b10, b11, b12, b13, b14, b15, b16, b17, b18, b19, b20, b21, b22, b23, b24, b25, b26, b27, b28, b29, b30, b31, b32, b33, b34, b35, b36, b37, b38, b39, b40, b41, b42, b43, b44, b45, b46, b47, b48, b49, b50, b51, b52, b53, b54, b55
Case Name Status Exec Time Memory
a01 AC 1 ms 256 KB
a02 AC 1 ms 256 KB
a03 AC 1 ms 256 KB
a04 AC 1 ms 256 KB
b05 AC 1 ms 256 KB
b06 AC 44 ms 45696 KB
b07 AC 43 ms 47616 KB
b08 AC 42 ms 45824 KB
b09 AC 42 ms 45824 KB
b10 AC 42 ms 45696 KB
b11 AC 42 ms 45696 KB
b12 AC 42 ms 45696 KB
b13 AC 42 ms 45696 KB
b14 AC 43 ms 45696 KB
b15 AC 42 ms 45824 KB
b16 AC 14 ms 23168 KB
b17 AC 2 ms 2688 KB
b18 AC 1 ms 256 KB
b19 AC 42 ms 45824 KB
b20 AC 42 ms 45824 KB
b21 AC 42 ms 45696 KB
b22 AC 42 ms 45824 KB
b23 AC 42 ms 45696 KB
b24 AC 42 ms 45824 KB
b25 AC 43 ms 47104 KB
b26 AC 43 ms 45696 KB
b27 AC 43 ms 47488 KB
b28 AC 43 ms 45696 KB
b29 AC 43 ms 47488 KB
b30 AC 44 ms 47488 KB
b31 AC 43 ms 47488 KB
b32 AC 43 ms 47488 KB
b33 AC 42 ms 45824 KB
b34 AC 42 ms 45824 KB
b35 AC 42 ms 45824 KB
b36 AC 42 ms 45824 KB
b37 AC 42 ms 45824 KB
b38 AC 42 ms 45824 KB
b39 AC 42 ms 45824 KB
b40 AC 42 ms 45824 KB
b41 AC 42 ms 45824 KB
b42 AC 42 ms 45824 KB
b43 AC 42 ms 45824 KB
b44 AC 42 ms 45824 KB
b45 AC 43 ms 47360 KB
b46 AC 43 ms 47488 KB
b47 AC 43 ms 47616 KB
b48 AC 43 ms 47616 KB
b49 AC 43 ms 47616 KB
b50 AC 43 ms 45696 KB
b51 AC 43 ms 45696 KB
b52 AC 43 ms 45696 KB
b53 AC 43 ms 45696 KB
b54 AC 43 ms 45696 KB
b55 AC 43 ms 46592 KB