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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. long long power(long long x, long long y, long long p){
  4.     long long res = 1;
  5. 	while(y>0){
  6.         if(y&1) res=(res*x)%p;
  7.         y=y>>1;
  8.         x=(x*x)%p;
  9.     }
  10.     return res;
  11. }
  12. long long mod(long long n,long long p){
  13.     return power(n, p - 2, p);
  14. }
  15. long long nCr(long long n, long long r, long long p){
  16.     if(n<r) return 0;
  17.     if(r==0) return 1;
  18.     long long a[n + 1];
  19.     a[0]=1;
  20.     for(int i=1;i<=n;i++) a[i]=(a[i-1]*i)%p;
  21.     return (a[n]*mod(a[r],p)%p*mod(a[n-r],p)%p)%p;
  22. }
  23. int main()
  24. {
  25. 	int t;
  26. 	cin>>t;
  27. 	while(t--){
  28. 	    long long a,b,p=1000000007;
  29. 	    cin>>a>>b;
  30. 	    cout<< nCr(a,b, p);
  31. 	    cout<<"\n";
  32. 	}
  33. }
Success #stdin #stdout 0.01s 5280KB
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358633491
https://ideone.com/iwZ05i
language:
C++14 (gcc 8.3)
created:
11 days ago
visibility:
public

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