48 lines
1.1 KiB
C++
48 lines
1.1 KiB
C++
//不初始化你给我死全家
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#include<iostream>
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#include<cstdio>
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#include<cmath>
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#include<cstring>
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#include<algorithm>
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#include<cstdlib>
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using namespace std;
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#define MS(x,y) memset(x,y,sizeof(x))
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#define MP(x,y) make_pair(x,y)
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#define lowbit(x) (x&(-x))
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typedef long long LL;
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inline void fre1(){freopen("input.txt","r",stdin);/*freopen("output.txt","w",stdout);*/}
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inline void fre2(){fclose(stdin);/*fclose(stdout);*/}
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const int MAXN=30+5;
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const double EPS=1e-8;
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const int MOD=1e9+7;
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LL fact[MAXN*MAXN],C[MAXN][MAXN],dp[MAXN][MAXN];
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int main()
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{
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int n=11;
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fact[0]=1;
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for(int i=1;i<=n*n;++i) fact[i]=fact[i-1]*3%MOD;
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C[0][0]=1;
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for(int i=1;i<MAXN;++i){
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C[i][0]=C[i][i]=1;
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for(int j=1;j<i;++j)
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C[i][j]=(C[i-1][j]+C[i-1][j-1])%MOD;
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}
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for(int i=1;i<=10;++i){
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for(int j=0;j<=10;++j){
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dp[i][j]=fact[i*j];
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if(i==1&&j==0) dp[i][j]=1;
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for(int ii=1;ii<=i;++ii){
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for(int jj=0;jj<=j;++jj){
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if(i==ii&&j==jj) continue;
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dp[i][j]-=C[i-1][ii-1]*C[j][jj]%MOD*dp[ii][jj]%MOD*fact[(i-ii)*(j-jj)]%MOD;
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dp[i][j]=(dp[i][j]%MOD+MOD)%MOD;
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}
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}
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}
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}
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int m;
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while(~scanf("%d%d",&n,&m)) printf("%I64d\n",dp[n][m]);
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return 0;
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}
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