How to Use pair in C++: Syntax and Examples

In C++, std::pair is a simple container that holds two values of possibly different types together. You create a pair using std::make_pair or by directly initializing it with two values, then access the elements using first and second members.

Syntax

The std::pair template holds two values called first and second. You can create a pair by specifying the types and initializing the values.

• std::pair<Type1, Type2> p(value1, value2); creates a pair with two values.
• auto p = std::make_pair(value1, value2); creates a pair with types deduced automatically.
• Access elements with p.first and p.second.

cpp

std::pair<Type1, Type2> p(value1, value2);
auto p2 = std::make_pair(value1, value2);
// Access elements
p.first;
p.second;

Example

This example shows how to create a pair of a string and an integer, then print both values.

cpp

#include <iostream>
#include <utility> // for std::pair and std::make_pair
#include <string>

int main() {
    std::pair<std::string, int> person = std::make_pair("Alice", 30);
    std::cout << "Name: " << person.first << "\n";
    std::cout << "Age: " << person.second << "\n";
    return 0;
}

Output

Name: Alice
Age: 30

Common Pitfalls

Common mistakes when using std::pair include:

• Forgetting to include the <utility> header.
• Mixing up first and second elements.
• Assuming pairs can hold more than two values (use std::tuple for that).
• Not specifying types explicitly when needed, causing compilation errors.

cpp

#include <iostream>
// Missing #include <utility> causes error

int main() {
    // Wrong: no #include <utility>
    // std::pair<int, int> p(1, 2); // Error: 'pair' not declared

    // Correct:
    std::pair<int, int> p(1, 2);
    std::cout << p.first << ", " << p.second << "\n";
    return 0;
}

Quick Reference

Feature	Description
std::pair	Template to hold two values of types Type1 and Type2
std::make_pair(value1, value2)	Creates a pair with types deduced from values
p.first	Access the first element of the pair
p.second	Access the second element of the pair
Use header	Required to use std::pair and std::make_pair

Key Takeaways

Use std::pair to store two related values together with different types.

Create pairs with std::make_pair or direct initialization.

Access elements using .first and .second members.

Always include the header to use std::pair.

For more than two values, consider std::tuple instead.