stl::pair Example

Example: Using pair to Represent and Manipulate (x, y) Coordinates

Here’s a C++ program that demonstrates how to use pair to store and manipulate (x, y) coordinates.

#include <iostream>
#include <vector>
#include <utility> // For pair
#include <cmath>   // For sqrt()

using namespace std;

// Function to calculate the distance between two coordinates
double calculateDistance(pair<int, int> point1, pair<int, int> point2) {
    int dx = point2.first - point1.first;
    int dy = point2.second - point1.second;
    return sqrt(dx * dx + dy * dy);
}

int main() {
    // Representing coordinates using pairs
    pair<int, int> pointA = {3, 4};
    pair<int, int> pointB = {7, 1};

    // Displaying the coordinates
    cout << "Point A: (" << pointA.first << ", " << pointA.second << ")\n";
    cout << "Point B: (" << pointB.first << ", " << pointB.second << ")\n";

    // Calculating the distance between two points
    double distance = calculateDistance(pointA, pointB);
    cout << "Distance between Point A and Point B: " << distance << endl;

    // Storing multiple points in a vector of pairs
    vector<pair<int, int>> points = {{1, 2}, {3, 4}, {5, 6}};
    
    // Adding a new point
    points.push_back({7, 8});

    // Displaying all points
    cout << "\nAll Points:\n";
    for (const auto& point : points) {
        cout << "(" << point.first << ", " << point.second << ")\n";
    }

    // Finding and displaying the midpoint of the first two points
    pair<int, int> midpoint = {
        (pointA.first + pointB.first) / 2,
        (pointA.second + pointB.second) / 2
    };
    cout << "\nMidpoint of Point A and Point B: (" << midpoint.first << ", " << midpoint.second << ")\n";

    return 0;
}

Explanation:

1. Storing Coordinates:
   • Pairs are used to represent (x, y) coordinates. For example, pointA is {3, 4}.
2. Manipulating Coordinates:
   • The function calculateDistance computes the Euclidean distance between two points using the formula: distance=sqr((x₂−x₁)²+(y₂−y₁)²)
3. Storing Multiple Points:
   • A vector<pair<int, int>> is used to store multiple (x, y) coordinates.
4. Finding the Midpoint:
   • The midpoint between two points (x1, y1) and (x2, y2) is: midpoint= ((x₁​+x₂)/2​​,(y₁​+y₂)/2​​)

Sample Output:

Point A: (3, 4)
Point B: (7, 1)
Distance between Point A and Point B: 5

All Points:
(1, 2)
(3, 4)
(5, 6)
(7, 8)

Midpoint of Point A and Point B: (5, 2)

This example shows how to use pair to work with simple geometric data in C++.