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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. typedef long long ll;
  5. typedef vector<ll> vi;
  6. typedef vector<long long> vl;
  7. #define pb push_back
  8. #define ff first
  9. #define ss second
  10. #define forn(n) for (ll i = 0; i < n; i++)
  11. #define forc(cn, abc) ((cn).find(abc) != (cn).end())
  12. #define yes cout << "YES\n";
  13. #define no cout << "NO\n";
  14. #define all(a) a.begin(), a.end()
  15. #define rall(a) a.rbegin(), a.rend()
  16. #define poin(x) cout << fixed << setprecision(x);
  17.  
  18. vector<ll> dp(35);
  19. ll combination(ll n, ll r)
  20. {
  21.     if (n == r)
  22.         return 1;
  23.  
  24.     if (r == 1)
  25.         return n;
  26.  
  27.     return dp[n] = combination(n - 1, r) + combination(n - 1, r - 1);
  28. }
  29. void solve()
  30. {
  31.     ll n, r;
  32.     cin >> n >> r;
  33.  
  34.     ll output = combination(n, r);
  35.     cout << output << endl;
  36. }
  37.  
  38. int main()
  39. {
  40.     ios_base::sync_with_stdio(0);
  41.     cin.tie(0);
  42.  
  43.     ll t = 1;
  44.     while (t--)
  45.     {
  46.         solve();
  47.     }
  48.  
  49.     return 0;
  50. }
  51.  
Success #stdin #stdout 0.01s 5320KB
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https://ideone.com/atM2mw
language:
C++ (gcc 8.3)
created:
3 hours ago
visibility:
public

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