Submission #5275484

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Source Code Expand

#include<cstdio>
#include<iostream>
#include<cstring>
#define RG register
#define LL long long
using namespace std;
const LL mod=1e9+7;
int n,m;
LL dp[305][305][305];
inline int read(){
    char ch=getchar(); int x=0, f=1;
    while(ch<'0' || ch>'9'){if(ch=='-') f=-1; ch=getchar(); }
    while(ch>='0' && ch<='9'){x=x*10+ch-'0'; ch=getchar();  }
    return x*f;}
int main()
{
//  freopen("Road of the King.in","r",stdin);
    //freopen(".out","w",stdout);
    n=read(); m=read();
    dp[0][1][1]=1;
    for(RG int i=0;i<m;i++)
     for(RG int j=1;j<=n;j++)
      for(RG int k=1;k<=j;k++)
      {
            (dp[i+1][j+1][k]+=dp[i][j][k]*(n-j))%=mod;
            (dp[i+1][j][k]+=dp[i][j][k]*(j-k))%=mod;
            (dp[i+1][j][j]+=dp[i][j][k]*k)%=mod;
      }
    printf("%lld\n",dp[m][n][n]);
    //fclose(stdin); fclose(stdout);
    return 0;
}

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