? Recursion in C

Recursion is when a function calls itself to solve a smaller part of the problem. It continues until it reaches a base case (the stopping condition).

? Basic Syntax

c
() {    function();  // Recursive call}

To avoid infinite recursion, always define a base case!

? Example: Factorial Using Recursion

c
#include int factorial(int n) {    () {    int num = 5;    printf("Factorial of %d is %d\n", num, factorial(num));    return 0;}

? Output:

csharp
Factorial of 5 is 120

? Key Concepts

• Base case: Stops the recursion (e.g., if (n == 0)).

• Recursive case: Function calls itself (e.g., n * factorial(n - 1)).

? Another Example: Fibonacci Series

c
int fibonacci(int n) {    if (n == 0) return 0;    if (n == 1) return 1;    return fibonacci(n - 1) + fibonacci(n - 2);}

?? When to Avoid Recursion

• Recursion can lead to stack overflow for deep recursion.

• Iteration is often more efficient in C.

? Tip:

Use recursion when a problem can be broken into smaller similar subproblems, like:

• Factorial

• Fibonacci

• Tree traversal

• Tower of Hanoi

• Searching/sorting algorithms (quick sort, merge sort)