unordered_map in c++

The unordered_map in C++ is an associative container that maps unique keys to values. The elements in the unordered_map are not stored in any particular order, but organized using the hash table into buckets. Here are the steps to use unordered_map in C++:

  1. Include the header file for unordered_map: #include

  2. Create an unordered_map with the desired key and value types: std::unordered_map myMap;

  3. Insert key-value pairs into the unordered_map: myMap["Alice"] = 25; myMap["Bob"] = 30;

  4. Access and modify elements in the unordered_map: myMap["Alice"]++; // Increment Alice's age

  5. Check if a key exists in the unordered_map: if (myMap.find("Bob") != myMap.end()) { // Key "Bob" exists in the unordered_map }

  6. Iterate through the unordered_map using iterators: for (auto it = myMap.begin(); it != myMap.end(); ++it) { std::cout << it->first << " : " << it->second << std::endl; }

  7. Erase elements from the unordered_map: myMap.erase("Alice");

  8. Get the size of the unordered_map: int size = myMap.size();

  9. Clear all elements from the unordered_map: myMap.clear();

These are the basic steps for using the unordered_map in C++. It provides a flexible and efficient way to store key-value pairs with fast access and insertion times.