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  1.  
  2. #include <bits/stdc++.h>
  3. using namespace std;
  4.  
  5. int main() {
  6.     int n;
  7.     cin >> n;
  8.  
  9.     vector<int> arr(n);
  10.     for (int i = 0; i < n; i++)
  11.         cin >> arr[i];
  12.  
  13.     unordered_map<int, vector<pair<int, int>>> mp;
  14.  
  15.     for (int k = 2; k < n - 1; k++) {
  16.         int j = k - 1;
  17.  
  18.         // Store earlier pairs (i, j).
  19.         for (int i = 0; i < j; i++) {
  20.             int xr = arr[i] ^ arr[j];
  21.             mp[xr].push_back({i, j});
  22.         }
  23.  
  24.         // Find matching pairs (k, l).
  25.         for (int l = k + 1; l < n; l++) {
  26.             int target = arr[k] ^ arr[l];
  27.  
  28.             auto it = mp.find(target);
  29.  
  30.             if (it != mp.end()) {
  31.                 for (auto [i, j] : it->second) {
  32.                     cout << "[" << i + 1 << ","
  33.                          << j + 1 << ","
  34.                          << k + 1 << ","
  35.                          << l + 1 << "]\n";
  36.                 }
  37.             }
  38.         }
  39.     }
  40.  
  41.     return 0;
  42. }
  43.  
Success #stdin #stdout 0s 5324KB
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stdin
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4 
1 2 3 0
stdout
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[1,2,3,4]
https://ideone.com/lCKNYT
language:
C++14 (gcc 8.3)
created:
3 hours ago
visibility:
public

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