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  1. #include <cstdio>
  2. #include <algorithm>
  3. using namespace std;
  4.  
  5. const int MOD = 55566677;
  6.  
  7. int main(){
  8.     int P[60]={1};
  9.     for(int i=1;i<60;i++) P[i]=P[i-1]*1ll*i%MOD;
  10.     int n,m,x[25],y[25];
  11.     while(scanf("%d%d",&n,&m)==2){
  12.         for(int i=0;i<m;i++) scanf("%d%d",x+i,y+i);
  13.         for(int i=0;i<m;i++) for(int j=i+1;j<m;j++){
  14.             if(x[i]==x[j] && y[i]==y[j]){
  15.                 swap(x[j],x[m-1]);
  16.                 swap(y[j],y[--m]);
  17.             }
  18.         }
  19.         int mask=(1<<m)-1,ans=P[n],s=0;
  20.         int pos[60]={},use[60]={},cnt=0,err=0;
  21.         for(int c=1;c<=mask;c++){
  22.             int i=__builtin_ctz(c);
  23.             s^=1<<i;
  24.             if(1<<i&s){
  25.                 cnt++;
  26.                 if(pos[x[i]]++==1) err++;
  27.                 if(use[y[i]]++==1) err++;
  28.             }else{
  29.                 cnt--;
  30.                 if(--pos[x[i]]==1) err--;
  31.                 if(--use[y[i]]==1) err--;
  32.             }
  33.             if(err) continue;
  34.             if(cnt&1) ans-=P[n-cnt]; else ans+=P[n-cnt];
  35.             if(ans<0) ans+=MOD;
  36.             if(ans>=MOD) ans-=MOD;
  37.         }
  38.         printf("%d\n",ans);
  39.     }
  40. }
  41.  
Not running #stdin #stdout 0s 0KB
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https://ideone.com/16bETS
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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