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  1. #include <iostream>
  2. #include <unordered_map>
  3. #include <utility>
  4.  
  5. // Custom hash function for std::pair<int, int>
  6. struct PairHash {
  7.     size_t operator()(const std::pair<int, int>& p) const {
  8.         // Combine the hashes of the two integers
  9.         size_t hash1 = std::hash<int>{}(p.first);
  10.         size_t hash2 = std::hash<int>{}(p.second);
  11.         // A simple way to combine the hashes is to XOR them
  12.         return hash1 ^ (hash2 << 1); // Shifting hash2 to avoid collisions when both integers are the same
  13.     }
  14. };
  15.  
  16. int main() {
  17.     std::unordered_map<std::pair<int, int>, int, PairHash> myMap;
  18.  
  19.     // Inserting values
  20.     myMap[std::make_pair(1, 2)] = 5;
  21.     myMap[std::make_pair(3, 4)] = 10;
  22.  
  23.     // Accessing values
  24.     std::cout << "Value of (1, 2): " << myMap[std::make_pair(1, 2)] << std::endl;
  25.     std::cout << "Value of (3, 4): " << myMap[std::make_pair(3, 4)] << std::endl;
  26.  
  27.     return 0;
  28. }
  29.  
Success #stdin #stdout 0s 5304KB
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stdin
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Standard input is empty
stdout
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Value of (1, 2): 5
Value of (3, 4): 10
https://ideone.com/Ahm5so
language:
C++14 (gcc 8.3)
created:
34 days ago
visibility:
public

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