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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define int long long 
  4. vector<int> vec;
  5. int n;
  6.  
  7. int recur(int l, int r) {
  8.     int ans = 0;
  9.     if (l + 1 >= r) {
  10.         return ans;
  11.     }
  12.     int mid = (l + r) / 2;
  13.     ans += recur(l, mid);
  14.     ans += recur(mid, r);
  15.  
  16.     // Debugging output
  17.     // cout << l << " " << r << endl;
  18.  
  19.     // Count inversions
  20.     int i = l, j = mid;
  21.     int k = 0;
  22.     int ans1 = 0; 
  23.     while (j < r) {
  24.         if(i + 1 == mid || vec[j] > vec[i]){
  25.             // while(vec[k] < vec[j]){
  26.             //     ans1 -= vec[k];
  27.             //     k++;
  28.             // }
  29.             ans += vec[j] * (i - k) + ans1;
  30.             // cout << ans << " " << k << endl; 
  31.             // cout << ans << " " << vec[j] << " " << ans1 << endl; 
  32.             j++;
  33.         	continue;
  34.         }
  35.         if (vec[i] > vec[j]) {
  36.             i++;
  37.             ans1 += vec[i];
  38.             cout << vec[i] << " ";
  39.  
  40.         } 
  41.     }
  42.     cout << endl; 
  43.  
  44.  
  45.     inplace_merge(vec.begin() + l, vec.begin() + mid, vec.begin() + r);
  46.     return ans;
  47. }
  48.  
  49. signed main() {
  50.     cin >> n;
  51.     vec.resize(n);
  52.     for (int i = 0; i < n; i++) {
  53.         cin >> vec[i];
  54.     }
  55.     cout << recur(0, n) << endl;
  56. }
Success #stdin #stdout 0.01s 5288KB
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https://ideone.com/n9CCEO
language:
C++14 (gcc 8.3)
created:
2 days ago
visibility:
public

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