How to Print a Map in C++ - Step by Step Examples

How to Print a Map in C++ ?

Answer

To print a map in C++, you can iterate over the map using a range-based for loop or an iterator and print each key-value pair.

✐ Examples

1 Printing a Map Using Range-Based For Loop

We can print a map in C++ by iterating over the map using a range-based for loop and printing each key-value pair.

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 then 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 a range-based for loop to iterate over each key-value pair in the map. The loop variable pair represents each key-value pair in the map.
Inside the loop, we print the key and value of each pair using std::cout.

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"}
    };

    // Print the map using a range-based for loop
    for (const auto& pair : myMap) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}

Output

1: one
2: two
3: three

2 Printing a Map Using Iterator

We can print a map in C++ by iterating over the map using an iterator and printing each key-value pair.

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 then declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We declare an iterator of type std::map<int, std::string>::iterator and initialize it to the beginning of the map using the begin() method.
We use a while loop to iterate over the map until the iterator reaches the end of the map. Inside the loop, we print the key and value of each pair using std::cout and increment the iterator to move to the next pair.

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"}
    };

    // Declare an iterator
    std::map<int, std::string>::iterator it = myMap.begin();

    // Print the map using an iterator
    while (it != myMap.end()) {
        std::cout << it->first << ": " << it->second << std::endl;
        ++it;
    }

    return 0;
}

Output

1: one
2: two
3: three

3 Printing a Map Using for_each and Lambda Function

We can print a map in C++ by using the std::for_each algorithm along with a lambda function to print each key-value pair.

For example,

We start by including the <map>, <iostream>, and <algorithm> header files, which provide the necessary functions and data structures for working with maps, input-output operations, and algorithms.
We then 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 std::for_each algorithm to iterate over the map. The algorithm takes two iterators (begin and end of the map) and a lambda function that defines the operation to be performed on each element.
The lambda function takes a key-value pair as an argument and prints the key and value using std::cout.

C++ Program

#include <map>
#include <iostream>
#include <algorithm>

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

    // Print the map using for_each and a lambda function
    std::for_each(myMap.begin(), myMap.end(), [](const std::pair<int, std::string>& pair) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    });

    return 0;
}

Output

1: one
2: two
3: three

Summary

In this tutorial, we learned How to Print a Map in C++ language with well detailed examples.

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How to Print a Map in C++ - Step by Step Examples