Recursion vs Iteration When Each Wins in DSA C - Build Both Approaches

Recursion vs Iteration: When Each Wins

📖 Scenario: Imagine you are helping a friend understand two ways to solve problems: recursion and iteration. You will create simple C programs to see how each method works and when one might be better than the other.

🎯 Goal: Build two C functions to calculate the factorial of a number: one using recursion and one using iteration. Then compare their outputs for the same input.

📋 What You'll Learn

Create a variable called number with the value 5

Write a recursive function called factorial_recursive that takes an int n and returns the factorial of n

Write an iterative function called factorial_iterative that takes an int n and returns the factorial of n

Print the results of both functions for the variable number

💡 Why This Matters

🌍 Real World

Understanding recursion and iteration helps solve many programming problems like searching, sorting, and navigating data structures.

💼 Career

Many software jobs require knowing when to use recursion or iteration for efficient and clear code.

1

Create the input variable

Create an integer variable called number and set it to 5.

DSA C

#include 

int main() {
    // Create an integer variable called number and set it to 5
    // Your code here

    return 0;
}

Hint

Use int number = 5; inside the main function.

2

Write the recursive factorial function

Write a recursive function called factorial_recursive that takes an integer n and returns the factorial of n. Use the base case if (n == 0) to return 1, else return n * factorial_recursive(n - 1).

DSA C

#include 

// Write the recursive factorial function here
// Your code here

int main() {
    int number = 5;

    return 0;
}

Hint

Remember the base case for factorial is when n == 0.

3

Write the iterative factorial function

Write an iterative function called factorial_iterative that takes an integer n and returns the factorial of n. Use a for loop to multiply numbers from 1 to n.

DSA C

#include 

int factorial_recursive(int n) {
    if (n == 0) {
        return 1;
    } else {
        return n * factorial_recursive(n - 1);
    }
}

// Write the iterative factorial function here
// Your code here

int main() {
    int number = 5;

    return 0;
}

Hint

Use a for loop from 1 to n multiplying a result variable.

4

Print the factorial results

Print the factorial of number using both factorial_recursive and factorial_iterative functions. Use printf to show the results with labels.

DSA C

#include 

int factorial_recursive(int n) {
    if (n == 0) {
        return 1;
    } else {
        return n * factorial_recursive(n - 1);
    }
}

int factorial_iterative(int n) {
    int result = 1;
    for (int i = 1; i <= n; i++) {
        result *= i;
    }
    return result;
}

int main() {
    int number = 5;

    // Print the factorial results using both functions
    // Your code here

    return 0;
}

Hint

Use printf with the format "Recursive factorial of %d is %d\n" and call factorial_recursive(number). Do the same for factorial_iterative.