C Recursion

 C Recursion Tutorial

Recursion in C language is a technique where a function calls itself to solve a problem by breaking it into smaller sub-problems.

What is Recursion?

A function that calls itself directly or indirectly is called a recursive function.

Every recursive function must have:

1. Base condition (stopping case)

2. Recursive call (self call)

 Basic Recursion Syntax

 Simple Recursion Example

Print Numbers 1 to 5

 Output: 1 2 3 4 5

 Factorial Using Recursion (Interview Favorite)

 5! = 120

 Fibonacci Series Using Recursion

•  Inefficient for large values

 Recursion vs Iteration

•  Use recursion when logic is naturally recursive

Stack Working in Recursion (Very Important)

Each recursive call:

• Gets its own stack frame

• Stores local variables & return address

 Deep recursion → Stack overflow

 Tail Recursion (Advanced)

 Indirect Recursion

 Common Mistakes

•  Missing base condition
•  Infinite recursion
•  Large input causing stack overflow
•  Wrong return logic

 Interview Questions (Must Prepare)

1. What is recursion?

2. Base condition importance?

3. Difference between recursion & iteration

4. What is stack overflow?

5. Tail recursion

6. Indirect recursion

 Real-Life Use Cases

• Tree & graph traversal

• Divide & conquer algorithms

• Backtracking

• Compiler design

• OS process handling

Summary

•  Recursion simplifies complex problems
•  Requires proper base condition
•  Uses stack memory
•  Very important for DSA & interviews