How to Clear All Key-Value Pairs from a Map in C++ - Step by Step Examples

How to Clear All Key-Value Pairs from a Map in C++ ?

Answer

To clear all key-value pairs from a map in C++, you can use the clear method. This method removes all elements from the map, leaving it empty.

✐ Examples

1 Clearing All Key-Value Pairs Using clear Method

We can clear all key-value pairs from a map in C++ using the clear method, which removes all elements from the map.

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 clear method to remove all key-value pairs from the map.
We print the size of the map using the size method to verify that the map is empty.

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"}
    };

    // Clear all key-value pairs using clear method
    myMap.clear();

    // Print the size of the map
    std::cout << "Size of the map after clearing: " << myMap.size() << std::endl;

    return 0;
}

Output

Size of the map after clearing: 0

2 Clearing an Already Empty Map

We can use the clear method on an already empty map in C++, and it will still leave the map empty.

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 an empty map named myMap. In this example, the map has integer keys and string values.
We use the clear method to remove all key-value pairs from the map, even though it is already empty.
We print the size of the map using the size method to verify that the map is still empty.

C++ Program

#include <map>
#include <iostream>

int main() {
    // Declare and initialize an empty map
    std::map<int, std::string> myMap;

    // Clear the map using clear method
    myMap.clear();

    // Print the size of the map
    std::cout << "Size of the map after clearing: " << myMap.size() << std::endl;

    return 0;
}

Output

Size of the map after clearing: 0

3 Clearing a Map After Inserting Elements

We can insert key-value pairs into a map and then clear all key-value pairs using the clear method.

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 and insert some key-value pairs into it. In this example, the map has integer keys and string values.
We use the clear method to remove all key-value pairs from the map.
We print the size of the map using the size method to verify that the map is empty.

C++ Program

#include <map>
#include <iostream>

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

    // Clear all key-value pairs using clear method
    myMap.clear();

    // Print the size of the map
    std::cout << "Size of the map after clearing: " << myMap.size() << std::endl;

    return 0;
}

Output

Size of the map after clearing: 0

Summary

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

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How to Clear All Key-Value Pairs from a Map in C++ - Step by Step Examples