How to create an unordered_map with pair as key in C++
Dec 17, 2020
Step 1: Define Structure.
struct hash_pair {
template <class T1, class T2>
size_t operator()(const pair<T1, T2>& p) const
{
auto hash1 = hash<T1>{}(p.first);
auto hash2 = hash<T2>{}(p.second);
return hash1 ^ hash2;
}
};
Step 2: Declare this way
unordered_map<pair<int, int>, bool, hash_pair> um;