C++ Program to find the LCM of two numbers

Program to find the LCM of two numbers

Here we will discuss how to find the LCM of two numbers entered by the user in c++ programming language.

LCM, or least common multiple in mathematics,of two numbers is the smallest positive integer that is divisible by both the numbers.

For a reference let’s find LCM of 6 and 7

  • Multiples of 6 are 6, 12, 18, 24, 30, 36, 42, 48…
  • Multiples of 7 are 7, 14, 21, 28, 35, 42, 47, 54…

As we can see the lowest or least common multiple of 6 and 7 is 42

There are many approaches to find the LCM of two numbers like recursion, loops, etc. Here we are using the recursion method.

Program to find LCM of two numbers

Algorithm:-

  1. The user gives two numbers as inputs.
  2. The input is stored in two int type variables say first and second.
  3. A function, findLCM is called to find the LCM with first and second as parameters.
    1. A static int variable fact is taken so that it only gets initialized once
    2. If fact is divisible for both numbers then fact is the LCM

                                       if( fact % first == 0 && fact % second == 0 )

               3. Otherwise following happens

      1. The value of fact is incremented

                                       fact=fact+first

      4. findLCM function is recursively called again

      5. A value that is returned is the LCM of two numbers entered by the user

C++ Code:-

    
    //C++ program
    //LCM of two numbers
    #include<iostream>
    using namespace std;
    int findLCM(int,int);
    //main program
    int main()
    {
            int first,second;
            cout<<“Enter first number : “;
            cin>>first;
            cout<<“Enter second number : “;
            cin>>second;
            //calling function to find lcm
            cout<<findLCM(first,second)<<” is the LCM of two numbers.”;
            return 0;
    }
    //function to find lcm
    int findLCM(int firstint second)
    {  
        static int fact = first;
        // if true then fact is the lcm
        if(fact % first == 0 && fact % second == 0)
        {
            return fact;
        }
        //if false call function again
        else
        {
            fact=fact + first;
            findLCM(first,second);
        }
        return fact;
    }

    Output:

    Enter first number : 8
    Enter second number : 14
    56 is the LCM of two numbers.
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