unordered_map for pairs

unordered_map_pair.cpp

@@ -0,0 +1,40 @@
+// https://www.geeksforgeeks.org/how-to-create-an-unordered_map-of-pairs-in-c/
+// CPP program to demonstrate implementation of
+// unordered_map for a pair.
+#include <bits/stdc++.h>
+using namespace std;
+
+// A hash function used to hash a pair of any kind
+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;
+	}
+};
+
+int main()
+{
+	// Sending the hash function as a third argument
+	unordered_map<pair<int, int>, bool, hash_pair> um;
+
+	// Creating some pairs to be used as keys
+	pair<int, int> p1(1000, 2000);
+	pair<int, int> p2(2000, 3000);
+	pair<int, int> p3(2005, 3005);
+
+	// Inserting values in the unordered_map.
+	um[p1] = true;
+	um[p2] = false;
+	um[p3] = true;
+
+	cout << "Contents of the unordered_map : \n";
+	for (auto p : um)
+		cout << "[" << (p.first).first << ", "
+			<< (p.first).second << "] ==> "
+			<< p.second << "\n";
+
+	return 0;
+}