Submission #6780480

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Source Code Expand

#include<bits/stdc++.h>


using namespace std;

int main(){
  int N;   cin >> N;
  vector<int > C(N);
  if ( N > 10){ return 0;}
  
  for(int i = 0 ; i <N; i++){ cin >> C[i];}
  
  vector<int> arr(N);
  for(int i = 0; i < N; i++){ arr[i] = i;}
  
  sort( C.begin(),C.end());
  
  long  double ans = 0; int cnt = 0;
    
    do{ cnt++; // N!　を表す
       double res = 0.0;
       vector<bool> flip( N, true);
       for(int i = 0; i < N - 1; i++){
         for(int j = i + 1; j < N; j++){
           if((C[arr[j]] % C[arr[i]] == 0)){ flip[arr[j]] = !flip[arr[j]];}
         }}
       
       for(int i = 0; i < N; i++){ 
         if( flip[i]){  res++;}} //表である枚数を数える
       
       ans += (double) res;
  
        
    } while(  next_permutation(arr.begin(),arr.end()));
      
 
  cout << fixed << setprecision(10) << ans / cnt<< endl;   return 0;}

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