Namaste Coders 👩‍💻

Before starting have a glance on the below article to know about functions in Python 👇

Built-in Functions User Defined Functions Lambda Functions

What is Recursion 🤔?

Recursion is simply self calling of a function. It is a technique of writing a function. In recursion we divide complex problem into simpler problem and than we find a solution for simpler problem which leads to solving the complex problem.

In recursion We have to think of following to solve a problem 👇

Base case: It will end the recursion and will provide the required answer
Simpler solution: It will lead towards complex problem solution.

Stacks are used behind the scene in recursion.

Example: We are going to learn how to find the factorial of a number. Suppose we need to find factorial of 5. 5!=54321

Recursively: Let’s make a function fact(num) which will take num as a parameter.

Simpler Solution: fact(num)=num*fact(num-1)

Base Case: if num=1 return 1

# Factorial of a number recursively

def fact(num):
    if(num==1):
        return 1
    ans=num*fact(num-1)
    return ans

num=5
ans=fact(num)
print("Factorial is :",num)

#Output:
#Factorial is : 5

Here is the tree structure of recursion. First, we go forward till the base case is hit. Then, it moves backward resulting into the output