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 .

Syntax:

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.



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// 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;
}

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Output:

20

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.

Reference:

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

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