How to Convert an Array of Key-Value Pairs to a Map in C++ - Step by Step Examples

How to Convert an Array of Key-Value Pairs to a Map in C++ ?

Answer

To convert an array of key-value pairs to a map in C++, you can iterate over the array and insert each key-value pair into the map. This method allows you to create a map from a collection of key-value pairs stored in an array.

✐ Examples

1 Converting a Vector of Pairs to a Map

We can convert a vector of key-value pairs to a map in C++ by iterating over the vector and inserting each key-value pair into the map.

For example,

We start by including the <map>, <vector>, and <iostream> headers, which provide the necessary functions and data structures for working with maps, vectors, and input-output operations.
We declare and initialize a vector of pairs named pairs with some key-value pairs. In this example, the pairs have integer keys and integer values.
We declare an empty map named myMap to store the key-value pairs.
We iterate over the vector using a range-based for loop and insert each key-value pair into the map using the insert method.
We print the resulting map to the console using a range-based for loop and the std::cout function to verify the conversion.

C++ Program

#include <map>
#include <vector>
#include <iostream>

int main() {
    // Declare and initialize a vector of pairs
    std::vector<std::pair<int, int>> pairs = {
        {1, 10},
        {2, 20},
        {3, 30},
        {4, 40},
        {5, 50}
    };

    // Declare an empty map to store the key-value pairs
    std::map<int, int> myMap;

    // Iterate over the vector and insert each pair into the map
    for (const auto& pair : pairs) {
        myMap.insert(pair);
    }

    // Print the resulting map
    std::cout << "Map from vector of pairs:\n";
    for (const auto& pair : myMap) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}

Output

Map from vector of pairs:
1: 10
2: 20
3: 30
4: 40
5: 50

2 Converting an Array of Structs to a Map

We can convert an array of structs with key-value members to a map in C++ by iterating over the array and inserting each struct's key-value pair into the map.

For example,

We start by including the <map>, <array>, and <iostream> headers, which provide the necessary functions and data structures for working with maps, arrays, and input-output operations.
We define a struct named Pair with integer members key and value.
We declare and initialize an array of Pair structs named pairs with some key-value pairs.
We declare an empty map named myMap to store the key-value pairs.
We iterate over the array using a range-based for loop and insert each struct's key-value pair into the map using the insert method.
We print the resulting map to the console using a range-based for loop and the std::cout function to verify the conversion.

C++ Program

#include <map>
#include <array>
#include <iostream>

struct Pair {
    int key;
    int value;
};

int main() {
    // Declare and initialize an array of structs
    std::array<Pair, 5> pairs = {
        Pair{1, 10},
        Pair{2, 20},
        Pair{3, 30},
        Pair{4, 40},
        Pair{5, 50}
    };

    // Declare an empty map to store the key-value pairs
    std::map<int, int> myMap;

    // Iterate over the array and insert each struct's key-value pair into the map
    for (const auto& pair : pairs) {
        myMap.insert({pair.key, pair.value});
    }

    // Print the resulting map
    std::cout << "Map from array of structs:\n";
    for (const auto& pair : myMap) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}

Output

Map from array of structs:
1: 10
2: 20
3: 30
4: 40
5: 50

3 Converting a List of Tuples to a Map

We can convert a list of key-value tuples to a map in C++ by iterating over the list and inserting each tuple's key-value pair into the map.

For example,

We start by including the <map>, <list>, and <iostream> headers, which provide the necessary functions and data structures for working with maps, lists, and input-output operations.
We declare and initialize a list of tuples named pairs with some key-value pairs. In this example, the tuples have integer keys and integer values.
We declare an empty map named myMap to store the key-value pairs.
We iterate over the list using a range-based for loop and insert each tuple's key-value pair into the map using the insert method.
We print the resulting map to the console using a range-based for loop and the std::cout function to verify the conversion.

C++ Program

#include <map>
#include <list>
#include <iostream>

int main() {
    // Declare and initialize a list of tuples
    std::list<std::pair<int, int>> pairs = {
        {1, 10},
        {2, 20},
        {3, 30},
        {4, 40},
        {5, 50}
    };

    // Declare an empty map to store the key-value pairs
    std::map<int, int> myMap;

    // Iterate over the list and insert each tuple's key-value pair into the map
    for (const auto& pair : pairs) {
        myMap.insert(pair);
    }

    // Print the resulting map
    std::cout << "Map from list of tuples:\n";
    for (const auto& pair : myMap) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}

Output

Map from list of tuples:
1: 10
2: 20
3: 30
4: 40
5: 50

Summary

In this tutorial, we learned How to Convert an Array of Key-Value Pairs to a Map in C++ language with well detailed examples.

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