How to create a Map with Initial Key-Value Pairs in C++ - Step by Step Examples

How to create a Map with Initial Key-Value Pairs in C++ ?

Answer

To create a map with initial key-value pairs in C++, you can use the std::map constructor with an initializer list. This creates a new map object with predefined key-value pairs.

✐ Examples

1 Creating a Map with Initial Key-Value Pairs

We can create a map in C++ with initial key-value pairs using the std::map constructor and an initializer list.

For example,

We start by including the <map> header file, which provides the necessary functions and data structures for working with maps.
We then declare a variable named myMap of type std::map. This variable will hold our map with initial key-value pairs.
We use the std::map constructor with an initializer list to create a new map object. In C++, the std::map constructor can take an initializer list to initialize the map with predefined key-value pairs.
The newly created map is now assigned to the myMap variable. In this example, the map has integer keys and string values.
We can now perform various operations on this map, such as adding more key-value pairs, checking for the presence of keys, and retrieving values.

C++ Program

#include <map>
#include <iostream>

int main() {
    // Declare a map with initial key-value pairs
    std::map<int, std::string> myMap = {
        {1, "one"},
        {2, "two"},
        {3, "three"}
    };

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

    return 0;
}

Output

1: one
2: two
3: three

2 Creating a Map with Different Key-Value Types

We can create a map in C++ with initial key-value pairs of different types using the std::map constructor and an initializer list.

For example,

We start by including the <map> header file, which provides the necessary functions and data structures for working with maps.
We then declare a variable named studentGrades of type std::map. This variable will hold our map with initial key-value pairs where keys are strings (student names) and values are characters (grades).
We use the std::map constructor with an initializer list to create a new map object. In C++, the std::map constructor can take an initializer list to initialize the map with predefined key-value pairs.
The newly created map is now assigned to the studentGrades variable. In this example, the map has string keys and char values.
We can now perform various operations on this map, such as adding more key-value pairs, checking for the presence of keys, and retrieving values.

C++ Program

#include <map>
#include <iostream>

int main() {
    // Declare a map with initial key-value pairs
    std::map<std::string, char> studentGrades = {
        {"Alice", 'A'},
        {"Bob", 'B'},
        {"Charlie", 'C'}
    };

    // Operations on the map
    for(const auto& pair : studentGrades) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}

Output

Alice: A
Bob: B
Charlie: C

3 Creating a Map with Integer Keys and Float Values

We can create a map in C++ with initial key-value pairs where keys are integers and values are floats using the std::map constructor and an initializer list.

For example,

We start by including the <map> header file, which provides the necessary functions and data structures for working with maps.
We then declare a variable named productPrices of type std::map. This variable will hold our map with initial key-value pairs where keys are integers (product IDs) and values are floats (prices).
We use the std::map constructor with an initializer list to create a new map object. In C++, the std::map constructor can take an initializer list to initialize the map with predefined key-value pairs.
The newly created map is now assigned to the productPrices variable. In this example, the map has integer keys and float values.
We can now perform various operations on this map, such as adding more key-value pairs, checking for the presence of keys, and retrieving values.

C++ Program

#include <map>
#include <iostream>

int main() {
    // Declare a map with initial key-value pairs
    std::map<int, float> productPrices = {
        {101, 29.99},
        {102, 39.99},
        {103, 49.99}
    };

    // Operations on the map
    for(const auto& pair : productPrices) {
        std::cout << "Product " << pair.first << ": $" << pair.second << std::endl;
    }

    return 0;
}

Output

Product 101: $29.99
Product 102: $39.99
Product 103: $49.99

Summary

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

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How to create a Map with Initial Key-Value Pairs in C++ - Step by Step Examples