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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.  
  29. //* Case 2 : n <= 1e9  &&  r <= 20
  30.  
  31. int nCr(int n, int r){
  32. 	if(r>n || r<0) return 0;
  33.  
  34. 	int a = 1;
  35. 	for(int i=1; i<=r; i++){
  36. 		a = (a * n)%M;
  37. 		n--;
  38. 	}
  39.  
  40. 	int factR = 1;
  41. 	for(int i=2; i<=r; i++){
  42. 		factR = (factR * i)%M;
  43. 	}
  44.  
  45. 	//* 1/r!    =>       (r!)^(M-2)
  46. 	return (a%M * power(factR, M-2, M)  ) % M;
  47. }
  48.  
  49.  
  50. int consistency(int n, int r){
  51.  
  52. 	return nCr(n, r);
  53.  
  54. }
  55.  
  56.  
  57.  
  58.  
  59.  
  60.  
  61.  
  62.  
  63.  
  64.  
  65.  
  66.  
  67.  
  68.  
  69.  
  70. int practice(int n, int r){
  71.  
  72.  
  73.  
  74.     return 0;
  75. }
  76.  
  77.  
  78.  
  79.  
  80.  
  81. void solve() {
  82.  
  83.     int n, r;
  84.     cin>> n >> r;
  85.  
  86.  
  87.     cout << consistency(n, r) << endl;
  88.  
  89.  
  90. }
  91.  
  92.  
  93.  
  94.  
  95.  
  96. int32_t main() {
  97.     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  98.  
  99.     int t = 1;
  100.     cin >> t;
  101.     while (t--) {
  102.         solve();
  103.     }
  104.  
  105.     return 0;
  106. }
Success #stdin #stdout 0s 5312KB
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https://ideone.com/zNev8z
language:
C++14 (gcc 8.3)
created:
20 hours ago
visibility:
public

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