How to Remove a Key-Value Pair from a Map in C++ - Step by Step Examples

How to Remove a Key-Value Pair from a Map in C++ ?

Answer

To remove a key-value pair from a map in C++, you can use the erase method. This method allows you to remove the key-value pair associated with the specified key.

✐ Examples

1 Removing a Key-Value Pair Using erase Method

We can remove a key-value pair from a map in C++ using the erase method, which removes the key-value pair associated with the specified key.

For example,

We start by including the <map> and <iostream> header files, which provide the necessary functions and data structures for working with maps and input-output operations.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We use the erase method to remove the key-value pair associated with the key 2. The erase method removes the key-value pair from the map.
We print the contents of the map to the console using a range-based for loop and std::cout to verify that the key-value pair has been removed.

C++ Program

#include <map>
#include <iostream>

int main() {
    // Declare and initialize a map
    std::map<int, std::string> myMap = {
        {1, "one"},
        {2, "two"},
        {3, "three"}
    };

    // Remove a key-value pair using erase method
    myMap.erase(2);

    // Print the contents of the map
    for (const auto& pair : myMap) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}

Output

1: one
3: three

2 Handling Key Not Found Using erase Method

We can handle the case where a key is not found in a map in C++ using the erase method, which does nothing if the key is not present.

For example,

We start by including the <map> and <iostream> header files, which provide the necessary functions and data structures for working with maps and input-output operations.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We use the erase method to attempt to remove the key-value pair associated with the key 4. The erase method does nothing if the key is not found.
We print the contents of the map to the console using a range-based for loop and std::cout to verify that the map is unchanged.

C++ Program

#include <map>
#include <iostream>

int main() {
    // Declare and initialize a map
    std::map<int, std::string> myMap = {
        {1, "one"},
        {2, "two"},
        {3, "three"}
    };

    // Attempt to remove a non-existent key-value pair using erase method
    myMap.erase(4);

    // Print the contents of the map
    for (const auto& pair : myMap) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}

Output

1: one
2: two
3: three

3 Removing Multiple Key-Value Pairs Using erase Method

We can remove multiple key-value pairs from a map in C++ using the erase method, which removes the key-value pairs associated with the specified keys.

For example,

We start by including the <map> and <iostream> header files, which provide the necessary functions and data structures for working with maps and input-output operations.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We use the erase method to remove the key-value pairs associated with the keys 1 and 3. The erase method removes the key-value pairs from the map.
We print the contents of the map to the console using a range-based for loop and std::cout to verify that the key-value pairs have been removed.

C++ Program

#include <map>
#include <iostream>

int main() {
    // Declare and initialize a map
    std::map<int, std::string> myMap = {
        {1, "one"},
        {2, "two"},
        {3, "three"}
    };

    // Remove multiple key-value pairs using erase method
    myMap.erase(1);
    myMap.erase(3);

    // Print the contents of the map
    for (const auto& pair : myMap) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}

Output

2: two

Summary

In this tutorial, we learned How to Remove a Key-Value Pair from a Map in C++ language with well detailed examples.

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How to Remove a Key-Value Pair from a Map in C++ - Step by Step Examples