Recursion Function

Last Updated: 02th September 2025

Recursion is a technique where a function calls itself to solve a problem. It is a way to break down a problem into smaller subproblem and solve them one by one.

Hinglish Tip 🗣: Ek aisa function jo khud to call kre,aur ek bade se problem ko ek ek chhote part me break kre.

🧱 Syntax Pattern

def func(params):
    if base_condition:
        return base_value          # 🛑 Stop
    return combine( func(smaller_params) )  # 🔁 Recurse with progress

Example 1.

# factorial
 def factorial(n):
    if n == 0 or n == 1:           # base case
        return 1
    return n * factorial(n - 1)    # recursive case

print(factorial(5))  # 120

Example 2.

# sum of list
def sum_list(nums):
    if not nums:            # base: empty list
        return 0
    return nums[0] + sum_list(nums[1:])

print(sum_list([3, 5, 7, 9]))  # 24

Example 3.

# Fibonacci sequence
def fibonacci(n):
    if n == 0:
        return 0
    if n == 1:
        return 1
    return fibonacci(n - 1) + fibonacci(n - 2)

print(fibonacci(6))  # 8

💡 Quick Practice

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