46 lines
1002 B
C++
46 lines
1002 B
C++
#include <iostream>
|
|
#include <cstdio>
|
|
#include <cstring>
|
|
#include <cstdlib>
|
|
#include <cmath>
|
|
#include <algorithm>
|
|
#define Mod 1000000007
|
|
#define lll __int64
|
|
using namespace std;
|
|
lll c[55][55];
|
|
lll dp[55][55];
|
|
void calc()
|
|
{
|
|
for(int i=0;i<=51;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;
|
|
}
|
|
}
|
|
int main()
|
|
{
|
|
int n,m,i,j,k,t;
|
|
calc();
|
|
while(scanf("%d%d",&n,&m)!=EOF)
|
|
{
|
|
memset(dp,0,sizeof(dp));
|
|
dp[0][0] = 1;
|
|
for(i=1;i<=n;i++)
|
|
{
|
|
for(k=1;k<=m;k++)
|
|
{
|
|
for(j=0;j<=k;j++)
|
|
{
|
|
for(t=max(1,k-j);t<=k;t++)
|
|
{
|
|
dp[i][k] = (dp[i][k]+dp[i-1][j]*c[m-j][k-j]%Mod*c[j][t-(k-j)]%Mod)%Mod;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
printf("%I64d\n",dp[n][m]%Mod);
|
|
}
|
|
return 0;
|
|
}
|