std::lcm in C++17

Competitive programming often involves computation of Least Common Multiple (LCM) of two numbers. One way of doing that is using boost::math::lcm(), which we discussed in the post – Inbuilt function for calculating LCM in C++ .
But, recently, C++ in its latest version C++17 has also included another in-built function for computation of LCM, std::lcm(). This function is defined inside the header file .


std::lcm (m, n)
Arguments: m, n
Returns: 0, if either of m or n are 0
         else, returns lcm of mod(m) and mod(n)

Remember, since this feature has been defined in latest version of C++, so using this function in compilers not supporting C++17, will throw an error.

// CPP program to illustrate
// std::lcm function of C++
#include <iostream>
#include <numeric>
using namespace std;
int main()
    cout << "LCM(10, 20) = " << std::lcm(10, 20)
         << endl;
    return 0;



Important Points:

  1. This function works on positive numbers, and if any argument is negative, it is firstly converted to its modulus, and then calculates the LCM.
  2. Also, it works only on integer data type , and if any other data type like char, double, is provided in its argument, then it will throw an error.


  1. C++ Weekly – Ep 67 – C++17’s std::gcd and std::lcm

This article is contributed by Mrigendra Singh. If you like GeeksforGeeks and would like to contribute, you can also write an article using or mail your article to See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

Attention reader! Don’t stop learning now. Get hold of all the important C++ Foundation and STL concepts with the C++ Foundation and STL courses at a student-friendly price and become industry ready.

Article Tags :
Practice Tags :