How to Remove Key-Value Pairs from a Map Based on Values in C++ - Step by Step Examples

How to Remove Key-Value Pairs from a Map Based on Values in C++ ?

Answer

To remove key-value pairs from a map in C++ based on values, you need to iterate through the map and check each value. If the value matches the specified condition, remove the corresponding key-value pair.

✐ Examples

1 Removing Key-Value Pairs with Specific Value

We can remove key-value pairs from a map in C++ by iterating through the map and removing pairs with a specific value.

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 iterate through the map using an iterator. For each key-value pair, we check if the value matches the specified value 'two'.
If the value matches, we use the erase method to remove 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 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"},
        {4, "two"}
    };

    // Remove key-value pairs with specific value
    for (auto it = myMap.begin(); it != myMap.end(); ) {
        if (it->second == "two") {
            it = myMap.erase(it);
        } else {
            ++it;
        }
    }

    // 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 Removing Key-Value Pairs with a Range of Values

We can remove key-value pairs from a map in C++ by iterating through the map and removing pairs with values within a specified range.

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 integer values.
We iterate through the map using an iterator. For each key-value pair, we check if the value falls within the specified range (e.g., between 2 and 3 inclusive).
If the value falls within the range, we use the erase method to remove 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 pairs have been removed.

C++ Program

#include <map>
#include <iostream>

int main() {
    // Declare and initialize a map
    std::map<int, int> myMap = {
        {1, 1},
        {2, 2},
        {3, 3},
        {4, 2}
    };

    // Remove key-value pairs with values in the range [2, 3]
    for (auto it = myMap.begin(); it != myMap.end(); ) {
        if (it->second >= 2 && it->second <= 3) {
            it = myMap.erase(it);
        } else {
            ++it;
        }
    }

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

    return 0;
}

Output

1: 1

3 Removing Key-Value Pairs with Condition-Based Values

We can remove key-value pairs from a map in C++ by iterating through the map and removing pairs with values that meet a specified condition.

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 iterate through the map using an iterator. For each key-value pair, we check if the value meets a specified condition (e.g., if the length of the string is 3).
If the condition is met, we use the erase method to remove 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 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"},
        {4, "four"}
    };

    // Remove key-value pairs where value length is 3
    for (auto it = myMap.begin(); it != myMap.end(); ) {
        if (it->second.length() == 3) {
            it = myMap.erase(it);
        } else {
            ++it;
        }
    }

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

    return 0;
}

Output

3: three
4: four

Summary

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

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How to Remove Key-Value Pairs from a Map Based on Values in C++ - Step by Step Examples