CPP

Tutorial for deque and pair

Include Headers

To use deque and pair, include the following headers:

• <deque> for deque
• <utility> for pair

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deque (Double-Ended Queue)

A deque (double-ended queue) is a sequence container that allows fast insertions and deletions at both the front and back. It provides dynamic array-like functionality with efficient operations at both ends.

Features of deque:

• Fast insertions and deletions at both ends (unlike vector, which is optimized for insertions at the back).
• Supports random access (like vector).
• Uses dynamically allocated fixed-size arrays, offering better performance in some cases than vector.

Syntax:

#include <iostream>
#include <deque>

int main() {
    std::deque<int> dq;

    // Adding elements
    dq.push_back(10);
    dq.push_back(20);
    dq.push_back(30);
    dq.push_back(40);

    // Displaying first and last elements
    std::cout << "Front element: " << dq.front() << std::endl;
    std::cout << "Back element: " << dq.back() << std::endl;

    // Removing elements
    dq.pop_front();
    dq.pop_front();

    std::cout << "Front element after popping: " << dq.front() << std::endl;
    std::cout << "Back element after popping: " << dq.back() << std::endl;
    
    return 0;
}

Output:

Front element: 10
Back element: 40
Front element after popping: 30
Back element after popping: 40

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pair

A pair is a container that holds two values together. It is part of the <utility> header and is useful for handling key-value pairs or returning multiple values from a function.

Features of pair:

• Stores two heterogeneous values.
• Elements can be accessed using .first and .second.
• Can be used in STL containers like vector<pair<int, int>>.

Syntax:

#include <iostream>
#include <utility>  // For std::pair

int main() {
    std::pair<int, std::string> p1(1, "Alice");
    std::pair<int, std::string> p2 = std::make_pair(2, "Bob");
    
    // Accessing pair values
    std::cout << "Pair 1: " << p1.first << ", " << p1.second << std::endl;
    std::cout << "Pair 2: " << p2.first << ", " << p2.second << std::endl;
    
    // Modifying values
    p1.first = 10;
    p1.second = "Charlie";
    std::cout << "Modified Pair 1: " << p1.first << ", " << p1.second << std::endl;
    
    return 0;
}

Output:

Pair 1: 1, Alice
Pair 2: 2, Bob
Modified Pair 1: 10, Charlie