task_033_recursion

Recursion

Explaination

This example demonstrates a classic use case for recursion to compute the factorial of a number. Let's break it down step by step.

1. Factorial Concept: Factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n. For example:

   • (3! = 3 \times 2 \times 1 = 6)
   • (4! = 4 \times 3 \times 2 \times 1 = 24) The factorial of 0 is defined to be 1, i.e., (0! = 1).

2. Definition of factorial Function:

   func factorial(x int) int {
       if x == 1 {
           fmt.Println("x is 1 now")
           return 1
       } else {
           fmt.Println("x is : ", x)
           return x * factorial(x-1)
       }
   }

   The function is designed to compute the factorial of an integer x. Here's how it works:

   • Base Case: If x is 1, the function prints "x is 1 now" and returns 1 because (1! = 1).
   • Recursive Case: Otherwise, it prints the current value of x and then makes a recursive call to compute the factorial of x-1. The result of this recursive call is then multiplied by x to get the factorial of x.

3. Execution Flow: Calling factorial(3) triggers the following flow:

   factorial(3) => 3 * factorial(2) 
                => 3 * (2 * factorial(1))
                => 3 * (2 * 1)
                => 6

   The console output will be:

   x is :  3
   x is :  2
   x is 1 now

   These print statements show the order in which the function processes values of x. The deepest level of recursion is reached when x becomes 1, after which the function starts returning values to the previous levels of the call stack.

4. Final Output: In the main function, the result of factorial(3) (which is 6) gets printed, so the final output will be:

   x is :  3
   x is :  2
   x is 1 now
   6

In summary, this code demonstrates a recursive approach to calculating the factorial of a number by breaking down the problem into smaller subproblems until a base case (when x is 1) is reached.

Output

$ go run main.go
x is :  3
x is :  2
x is 1 now
6