Submission #999044

#	Time	Username	Problem	Language	Result	Execution time	Memory
999044		vjudge1	Sumtree (INOI20_sumtree)	C++17	0 / 100	3 ms	3676 KiB

Main

#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9+7;
const int N = 2e5+10;
long long fact[N];
long long binpow(long long a, long long b) {
  long long ans = 1;
  while(b) {
    if(b&1) {
      ans=(ans*a)%mod;
    }
    a=(a*a)%mod;
    b>>=1;
  }
  return ans;
}
long long ncr(long long nn, long long rr) {
  if(rr > nn)return 0;
  long long ans = fact[nn];
  ans = (ans*binpow(fact[rr], mod-2))%mod;
  ans = (ans*binpow(fact[nn-rr], mod-2))%mod;
  return ans;
}
int main () {
  cin.tie(0)->sync_with_stdio(0);
  fact[0] = 1;
  for(int i = 1;i<N;i++)fact[i] = (fact[i-1]*i)%mod;
  int n, r;
  cin >> n >> r;
  cout << ncr(n+r-1, r) << "\n";
}

• Subtask 1: 0 / 10
• Subtask 2: 0 / 20
• Subtask 3: 0 / 20
• Subtask 4: 0 / 20
• Subtask 5: 0 / 30