From f1c2082b3f10e58798d43176c812da519c52aa65 Mon Sep 17 00:00:00 2001
From: Amin <amin.arabi@gmail.com>
Date: Fri, 18 Oct 2024 21:18:54 -0400
Subject: [PATCH] Create Recursion.md

Recursion added.
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+
+# Recursion in C++
+
+## Tutorial
+Recursion in C++ refers to a function that calls itself to solve smaller instances of a problem. This approach is especially useful when solving problems that can be broken down into sub-problems, like calculating factorials, traversing trees, or solving puzzles like the Tower of Hanoi.
+
+A recursive function consists of two main parts:
+1. **Base case**: A condition where the function stops calling itself.
+2. **Recursive case**: Where the function calls itself with a smaller version of the problem.
+
+For example, calculating the factorial of a number `n` (denoted as `n!`) can be solved recursively:
+- Base case: `0! = 1`
+- Recursive case: `n! = n * (n - 1)!`
+
+## Exercise
+Write a recursive function that calculates the factorial of a number `n`. The function should return `1` when `n` is `0` (base case), and for any other positive number `n`, it should return `n * factorial(n - 1)` (recursive case).
+
+## Tutorial Code
+```cpp
+#include <iostream>
+
+// Define a function that calculates the factorial of a number
+int factorial(int n) {
+    // Add base case and recursive call here
+}
+
+int main() {
+    int n;
+    std::cout << "Enter a number: ";
+    std::cin >> n;
+
+    std::cout << "Factorial of " << n << " is " << factorial(n) << std::endl;
+
+    return 0;
+}
+```
+
+## Expected Output
+```
+Enter a number: 5
+Factorial of 5 is 120
+```
+
+## Solution
+```cpp
+#include <iostream>
+
+// Function to calculate the factorial of a number
+int factorial(int n) {
+    if (n == 0)  // Base case
+        return 1;
+    else         // Recursive case
+        return n * factorial(n - 1);
+}
+
+int main() {
+    int n;
+    std::cout << "Enter a number: ";
+    std::cin >> n;
+
+    std::cout << "Factorial of " << n << " is " << factorial(n) << std::endl;
+
+    return 0;
+}
+```