C++ Program to find GCD of three numbers

August 23, 2021

C++ Program to find GCD of three numbers

Here, in this section we will discuss GCD of three numbers in C++. GCD (Greatest Common Divisor) of two numbers is the largest number that divides both numbers.

Example : The GCD of 20, 45 and 30 will be :

Factors of 20 are 2 X 2 X 5

Factors of 45 are 3 X 3 X 5

Factors of 30 are 2 X 3 X 5

Common factor of 20, 45 and 30 : 5 , So the required GCD will be 5

Algorithm :

Take the input of three numbers from the user.
Store them in variable a, b and c.
Find the maximum among the three.
Run a reverse loop from maximum number to 1.
Check for every number if all three number is divisible by that particular number or not.
If it is so then break the loop and print that number.

#include <iostream>
using namespace std;

int gcd (int a, int b, int c) 
{
  
  int maxi = 0;
  
  maxi = max(a, max(b, c));
  
  for(int i = maxi; i>1; i--)
  {
      if(( a%i == 0 ) and ( b%i == 0 ) and ( c%i == 0 ))
      {
          return i;
          break;
      }
  }
  
  return 1;
}

int main () 
{
  int a, b, c;
  
  cout<<"Enter the numbers :";
  cin >> a >> b >> c;
  
  
  
  cout << "GCD of " << a << ", " << b << " and " << c << " is " << gcd (a, b, c);
  
  return 0;
}

Output :

Enter the numbers : 20 45 30

GCD of 20, 45 and 30 is 5