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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define int              long long int
  4. #define double           long double
  5. #define print(a)         for(auto x : a) cout << x << " "; cout << endl
  6.  
  7.  
  8. const int M = 1000000007;
  9. const int N = 3e5+9;
  10. const int INF = 2e9+1;
  11. const int LINF = 2000000000000000001;
  12.  
  13. inline int power(int a, int b, int mod=M) {
  14.     int x = 1;
  15.     a %= mod;
  16.     while (b) {
  17.         if (b & 1) x = (x * a) % mod; 
  18.         a = (a * a) % mod;
  19.         b >>= 1;
  20.     }
  21.     return x;
  22. }
  23.  
  24.  
  25. //_ ***************************** START Below *******************************
  26.  
  27.  
  28. int nCr(int n, int r){
  29.     if(r<0 || r>n) return 0;
  30.  
  31.     int val = 1;
  32.     for(int i=1; i<=r; i++){
  33.         val = val * (n-i+1) / i;
  34.     }
  35.  
  36.     return val;
  37. }
  38.  
  39. int dearrange(int n){
  40.  
  41.     if(n==0) return 1;
  42.     else if(n==1) return 0;
  43.     else if(n==2) return 1;
  44.     else if(n==3) return 2;
  45.     else return 9;
  46. }
  47.  
  48. int consistency(int n, int k){
  49.  
  50.     int ans = 0;
  51.     for(int i=0; i<=k; i++){
  52.         ans += ((int)nCr(n,i) * dearrange(i));
  53.     }
  54.  
  55.     return ans;
  56. }
  57.  
  58.  
  59.  
  60.  
  61.  
  62.  
  63.  
  64.  
  65.  
  66.  
  67.  
  68.  
  69.  
  70.  
  71.  
  72. int practice(int n, int k){
  73.  
  74.  
  75.     return 0;
  76. }
  77.  
  78.  
  79.  
  80.  
  81.  
  82. void solve() {
  83.  
  84.     int n, k;
  85.     cin>> n >> k;
  86.  
  87.  
  88.     cout << consistency(n, k) << endl;
  89.  
  90.  
  91. }
  92.  
  93.  
  94.  
  95.  
  96.  
  97. int32_t main() {
  98.     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  99.  
  100.     int t = 1;
  101.     // cin >> t;
  102.     while (t--) {
  103.         solve();
  104.     }
  105.  
  106.     return 0;
  107. }
Success #stdin #stdout 0s 5316KB
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https://ideone.com/q64kmt
language:
C++14 (gcc 8.3)
created:
7 hours ago
visibility:
public

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