fork download
copy 
  1. #include <bits/stdc++.h>
  2. typedef long long ll;
  3. using namespace std;
  4. void Code_By_Mohamed_Khaled() {
  5.     ios_base::sync_with_stdio(false);
  6.     cin.tie(nullptr);
  7.     cout.tie(nullptr);
  8. #ifndef ONLINE_JUDGE
  9.     freopen("input.txt","r",stdin);
  10.     freopen("output.txt","w",stdout);
  11. #endif
  12. }
  13. ll mod =1e9+7;
  14. ll mul(ll a, ll b) { return ((b % mod) * (a % mod)) % mod; }
  15. ll add(ll a, ll b) { return ((b % mod) + (a % mod)) % mod; }
  16. ll fast_power(ll base,ll exp) {
  17.     ll result = 1;
  18.     while(exp > 0) {
  19.         if(exp & 1)
  20.             result=result*base%mod;
  21.         base=base*base%mod;
  22.         exp >>= 1;
  23.     }
  24.     return result;
  25. }
  26. vector<ll>fact(2e6+5,0),inv_fact(2e6+5);
  27. void precompute() {
  28.     fact[0]=fact[1]=1;ll N=2e6;
  29.     inv_fact[0]=1;
  30.     for (ll i=2;i<=2e6;i++) {
  31.         fact[i]=mul(fact[i-1],i);
  32.     }
  33.     inv_fact[N]=fast_power(fact[N],mod-2);
  34.     for (ll i=2e6-1;i>0;i--) {
  35.         inv_fact[i]=mul(inv_fact[i+1],i+1);
  36.     }
  37. }
  38. ll comb(int n, int r) {
  39.     if (r > n || r < 0) return 0;
  40.     return mul(mul(fact[n], inv_fact[r]), inv_fact[n - r]);
  41. }
  42. int main() {
  43.     Code_By_Mohamed_Khaled();
  44.     precompute();
  45.     ll h,w,a,b;cin>>h>>w>>a>>b;
  46.     ll ans=0;
  47.     for (int i = 0; i < w-b; i++){
  48.         ll ways1=comb((h-a-1)+(b+i),h-a-1);
  49.         ll ways2=comb((a-1)+(w-b-1-i),a-1);
  50.         ans=add(ans,mul(ways1,ways2));
  51.     }
  52.     cout<<ans<<"\n";
  53.     return 0;
  54. }
Success #stdin #stdout 0.18s 34272KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
0
https://ideone.com/01gBCz
language:
C++ (gcc 8.3)
created:
15 days ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!