Sunday, 15 December 2024

Python Coding challenge - Day 296| What is the output of the following Python Code?

Python Developer December 15, 2024 Python Coding Challenge No comments

Code Explanation:

Function Definition (factorial(n)):

The function factorial(n) is designed to calculate the factorial of a number n. The factorial of a number is the product of all positive integers less than or equal to that number. For example, 5! = 5 * 4 * 3 * 2 * 1 = 120.

Base Case (if n == 1:):

The line if n == 1: checks whether the number n is equal to 1.

If n is 1, the function returns 1. This is because the factorial of 1 is defined as 1. This is called the base case in recursion, which prevents the recursion from continuing indefinitely.

Recursive Case (return n * factorial(n-1)):

If n is not 1, the function proceeds to the line return n * factorial(n-1).

This is the recursive step, where the function calls itself with the value n-1 and multiplies the result by n.

The idea is that the factorial of n can be calculated as n * factorial(n-1). For example, to calculate 5!, the function will first calculate 4!, then multiply it by 5, and so on until it reaches the base case (factorial(1)).

First Call (factorial(5)):

When factorial(5) is called, n is 5, which is not equal to 1, so it proceeds to the recursive case and calls factorial(4).

The call stack becomes:

factorial(5) -> 5 * factorial(4)

factorial(4) -> 4 * factorial(3)

factorial(3) -> 3 * factorial(2)

factorial(2) -> 2 * factorial(1)

factorial(1) -> 1

Unwinding the Recursion:

Once factorial(1) returns 1, the recursion "unwinds" and each function call returns its result:

factorial(2) returns 2 * 1 = 2

factorial(3) returns 3 * 2 = 6