Find GCD of Two Numbers Using Recursion in Golang

In this tutorial, we will see how to find the Greatest common divisor of two numbers using the Golang language using recursion. We will see two ways to find the GCD of two numbers recursively. First will take more time where we are reducing the minimum of both numbers by 1 and then check if both the numbers are divisible by the min number or not. The second approach will take less time where we are subtracting the larger number from the smaller number until both numbers become equal.

Algorithm

• Step 1 - Declaring the variables to store the two numbers and answers.

• Step 2 - Initializing the variables.

• Step 3 - Call the function to find the GCD with the minimum number that will reduce each function call, do mod with both numbers, and return if the mod is zero.

• Step 4 - Printing the result.

Method 1: Non-Efficient Approach by using the Recursion function.

In this example, we are reducing the minimum of both numbers by 1 and then checking if both the numbers are divisible by the min number or not.

Example

package main

// fmt package provides the function to print anything
import (
   "fmt"
)

// this function finds the GCD of two numbers with three parameters
// of int type and have a return type of int type
func gcdOfTwoNumbers(number1, number2, minNumber int) int {

   // checking if the number minNumber can be divided by both number1, and number2
   if minNumber == 1 || (number1%minNumber == 0 && number2%minNumber == 0) {
      return minNumber
   }
   
   // returning the GCD
   return gcdOfTwoNumbers(number1, number2, minNumber-1)
}
func main() {

   // declaring the variable to store the value of two numbers
   // and a variable to store an answer
   var number1, number2, answer, minNumber int
   
   // initializing both the variables
   number1 = 20
   number2 = 15
   fmt.Println("Program to find the GCD of two numbers using the recursion function.")
   if number1 < number2 {
      minNumber = number1
   } else {
      minNumber = number2
   }
   
   // calling a function to find the GCD of two number
   // and passing a minimum of number1 and number2
   answer = gcdOfTwoNumbers(number1, number2, minNumber)
   
   // printing the result
   fmt.Println("The GCD of", number1, "and", number2, "is", answer)
}

Output

Program to find the GCD of two numbers using the recursion function.
The GCD of 20 and 15 is 5

Method 2: Efficient Approach by using the Recursion function

In this example, we will take less time by subtracting the larger number from the smaller number until both numbers become equal.

Example

package main

// fmt package provides the function to print anything
import (
   "fmt"
)

// this function finds the GCD of two numbers with two parameters
// of int type and have a return type of int type
func gcdOfTwoNumbers(number1, number2 int) int {

   // returning if both the numbers become equal
   if number1 == number2 {
      return number1
   }
   
   // reducing the lesser one with the greater one
   if number1 > number2 {
      number1 -= number2
   } else {
      number2 -= number1
   }
   
   // calling the function
   return gcdOfTwoNumbers(number1, number2)
}
func main() {

   // declaring the variable to store the value of two numbers
   // and a variable to store an answer
   var number1, number2, answer int
   
   // initializing both the variables
   number1 = 20
   number2 = 15
   fmt.Println("Program to find the GCD of two numbers in efficient way using the recursion function.")
   
   // calling a function to find the GCD of two number
   answer = gcdOfTwoNumbers(number1, number2)
   
   // printing the result
   fmt.Println("The GCD of", number1, "and", number2, "is", answer)
}

Output

Program to find the GCD of two numbers in an efficient way using the recursion function.
The GCD of 20 and 15 is 5

Conclusion

These are the different ways to find the GCD of two numbers using recursion. The second approach is more efficient than the first one. To learn more about go you can explore these tutorials.