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  1. #include<bits/stdc++.h>
  2.  
  3. using namespace std;
  4.  
  5. #define int long long
  6. #define double long double
  7. #define endl "\n"
  8. #define NAME "a"
  9.  
  10. const int MAXN = 1e3 + 5;
  11. const int MAXK = 1e3 + 5;
  12. const int inf = 1e18;
  13. const int MOD = 1e9 + 7;
  14.  
  15. void FileInput(){
  16.     if(fopen(NAME".inp" , "r") == NULL)
  17.         freopen(NAME".inp" , "w" , stdout);
  18.     freopen(NAME".inp" , "r" , stdin);
  19.     freopen(NAME".out" , "w" , stdout);
  20. }
  21.  
  22. int n , k;
  23. int a[MAXN];
  24. int f[MAXN][MAXK];
  25.  
  26. void solve(){
  27.     cin >> n >> k;
  28.     for(int i = 1 ; i <= n ; i++)    
  29.         cin >> a[i];
  30.  
  31.     f[0][0] = 1;
  32.     for(int i = 1 ; i <= n ; i++){
  33.         f[i][0] = 1;
  34.         for(int j = 1 ; j <= k ; j++){
  35.             f[i][j] = (f[i - 1][j - 1] * a[i] % MOD) + (f[i - 1][j] % MOD);
  36.             f[i][j] %= MOD;
  37.             // cout << i << " " << j << " " << f[i][j] << endl;
  38.         }
  39.     }
  40.  
  41.     cout << f[n][k] << endl;
  42. }
  43.  
  44. int32_t main(){
  45.    // FileInput();
  46.     ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
  47.     int t = 1;
  48.     // cin >> t;
  49.     while(t--)
  50.         solve();
  51.     return 0;
  52. }
Success #stdin #stdout 0s 5316KB
comments (?)
stdin 
Standard input is empty
stdout 
1
https://ideone.com/YSoC75
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

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