how to change the value of a key in hashmp in c++

To change the value of a key in a C++ unordered_map, you can follow these steps:

1. Access the desired key in the unordered_map using the square bracket operator ([]).
2. Assign the new value to the key.

Here's an example that demonstrates these steps:

#include <iostream>
#include <unordered_map>

int main() {
    std::unordered_map<std::string, int> myMap;

    // Insert some key-value pairs
    myMap["apple"] = 5;
    myMap["banana"] = 10;
    myMap["orange"] = 15;

    // Print the initial values
    std::cout << "Initial values:" << std::endl;
    for (const auto& pair : myMap) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    // Change the value of the "banana" key
    myMap["banana"] = 20;

    // Print the updated values
    std::cout << "Updated values:" << std::endl;
    for (const auto& pair : myMap) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}

Output:

Initial values:
orange: 15
banana: 10
apple: 5
Updated values:
orange: 15
banana: 20
apple: 5

In this example, we first create an unordered_map called myMap that maps strings to integers. We insert three key-value pairs into myMap. Then, we iterate over the map and print the initial values.

To change the value of the "banana" key, we use the square bracket operator myMap["banana"] and assign a new value of 20 to it. Finally, we iterate over the map again and print the updated values.

You can replace the types std::string and int with your desired key and value types in the actual code.