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Pair in C++

In C++, std::pair is a template class that allows you to store two values of different types as a single unit. It’s part of the C++ Standard Library and is commonly used in various situations where you need to represent a pair of values. Each value within the pair can have its own data type.

Here’s how to use std::pair:

#include <iostream>
#include <utility> // Include the utility header for std::pair

int main() {
    std::pair<int, double> myPair; // Declare a pair of int and double
    myPair.first = 42; // Assign a value to the first element of the pair
    myPair.second = 3.14; // Assign a value to the second element of the pair

    // Access the elements of the pair
    std::cout << "First element: " << myPair.first << std::endl;
    std::cout << "Second element: " << myPair.second << std::endl;

    // Create and initialize a pair
    std::pair<std::string, bool> status("OK", true);

    // Access elements using structured binding (C++17 and later)
    auto [message, success] = status;
    std::cout << "Message: " << message << ", Success: " << success << std::endl;

    return 0;
}

In this example:

  • We include the <utility> header to use std::pair.
  • We declare a std::pair named myPair with the first element of type int and the second element of type double.
  • We assign values to the first and second elements of myPair.
  • We access and print the elements of the pair using myPair.first and myPair.second.
  • We create and initialize another pair named status with a string and a boolean value.
  • We use structured binding (available in C++17 and later) to access and print the elements of the status pair.

std::pair is often used in situations where you need to return multiple values from a function, represent key-value pairs in associative containers (e.g., std::map), or store pairs of related data in various data structures. It provides a convenient way to bundle two values together.

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