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LCM of two numbers in C++

To find the least common multiple (LCM) of two numbers in C++, you can use the following code snippet. You can either implement a function to calculate the LCM or use the standard library’s std::lcm function introduced in C++17:

#include <iostream>
#include <numeric> // Required for std::lcm (C++17 and later)

int calculateLCM(int a, int b) {
    // Calculate LCM using the formula: LCM(a, b) = (a * b) / GCD(a, b)
    return (a * b) / std::__gcd(a, b);

int main() {
    int num1, num2;

    std::cout << "Enter the first number: ";
    std::cin >> num1;

    std::cout << "Enter the second number: ";
    std::cin >> num2;

    int lcm = calculateLCM(num1, num2);

    std::cout << "LCM of " << num1 << " and " << num2 << " is " << lcm << std::endl;

    return 0;

This code defines a function calculateLCM to compute the LCM of two numbers using the formula LCM(a, b) = (a * b) / GCD(a, b), where GCD is the greatest common divisor. It then uses this function in the main function to calculate and print the LCM of two user-input numbers.


The Tech Thunder

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