C++ Function Recursion

Function recursion in C++ is when a function calls itself to solve a problem. It breaks down a problem into smaller, simpler versions of itself until it reaches a base case, which stops the recursion.

A recursive function generally has two parts

Base Case: This is the condition where the recursion stops. Without a base case, the function would call itself indefinitely, causing a stack overflow.

Recursive Case: This is where the function calls itself to solve a smaller part of the problem.

General Structure of Recursive Function:

return_type function_name(parameters) {
    if (base_case_condition) {
        // Return result (or handle the simplest case)
    } else {
        // Recursive case (call the function itself)
        return function_name(smaller_sub_problem);
    }
}

Example: Factorial Function

The factorial of a number n is defined as:

• n! = n * (n – 1) * (n – 2) * … * 1
• Base case: 0! = 1

#include <iostream>
using namespace std;

int factorial(int n) {
    // Base case
    if (n == 0) {
        return 1;
    }
    // Recursive case
    return n * factorial(n - 1);
}

int main() {
    int num;
    cout << "Enter a number: ";
    cin >> num;
    cout << "Factorial of " << num << " is " << factorial(num) << endl;
    return 0;
}

Explanation:

1. The factorial function calls itself with n-1 until n reaches 0.
2. The base case (n == 0) returns 1, which stops further recursive calls.
3. The recursive case multiplies the current number n by the result of factorial(n - 1).

Output: