Recursion V/S Iteration

Published by: Anil K. Panta

Recursion vs Iteration

In programming, there are two ways to repeat tasks and solve problems step-by-step:

Recursion → A function calls itself
Iteration → A set of steps is repeated using loops (like for or while)

Let’s understand both with an easy example and compare their differences.

Example: Finding Factorial of a Number

The factorial of a number (n!) is the product of all natural numbers from 1 to n.

For example,

5! = 5 × 4 × 3 × 2 × 1 = 120

Program Using Recursion

#include <stdio.h>

int factorialUsingRecursion(int n) {

if (n == 0)

return 1; // Base case

return n * factorialUsingRecursion(n - 1); // Recursive call

}

Program Using Iteration

int factorialUsingIteration(int n) {

int res = 1;

for (int i = 2; i <= n; i++) {

res *= i; // Loop-based multiplication

}

return res;

}

int main() {

int num = 5;

printf("Factorial of %d using Recursion is: %d\n", num,

factorialUsingRecursion(num));

printf("Factorial of %d using Iteration is: %d", num,

factorialUsingIteration(num));

return 0;

}

Output:

Factorial of 5 using Recursion is: 120

Factorial of 5 using Iteration is: 120

Difference Between Recursion and Iteration

Here is a simple comparison table:

Feature	Recursion	Iteration
Definition	Function calls itself	Repeats using loops (for, while)
Used in	Tree, Graph traversal, TOH, etc.	Commonly used in most programming problems
Termination	By base case	By loop condition
Usage	Good for logic building, DP, Divide & Conquer	Preferred for performance and simplicity
Code size	Often shorter for recursive problems	Might be longer in naturally recursive tasks
Time complexity	Same or higher (due to repeated calls)	Often lower or same
Space complexity	Often higher (uses call stack)	Lower, no function call overhead
Overhead	Yes – due to function calls	No – runs directly in memory

Final Thought

Recursion is great for solving complex, logic-based problems like tree traversals and puzzles.
Iteration is faster and more memory-efficient for most everyday coding tasks.