added tutorial 18 cpp file from local machine

Author: SevenLinesOfCode

tut18.cpp

@@ -0,0 +1,76 @@
+#include <iostream>
+using namespace std;
+
+// Recursion(Reoccurence)
+// it is a method to to call itself directly or indirectly
+
+// Example
+// int sum(int num)
+// {
+//     if (num != 0)
+//     {
+//         return num + sum(num - 1);
+//     }
+//     return 0;
+// };
+
+// int factorial(int n)
+// {
+//     if (n > 1)
+//     {
+//         return n * factorial(n - 1);
+//     }
+//     else
+//     {
+//         return 1;
+//     }
+// };
+
+int fib(int n)
+{
+    if (n < 2)
+    {
+        return 1;
+    }
+    else
+    {
+        return fib(n - 2) + fib(n - 1);
+    }
+};
+
+int main()
+{
+    // Factorial of a number
+    // 6! = 6*5*4*3*2*1 = 720
+    // 0! = 1
+    // n! = n*(n-1)!
+
+    // Recursion Example 1
+
+    // int num;
+    // cout << "Enter the number : ";
+    // cin >> num;
+    // cout << "Sum is : " << sum(num);
+
+
+    // Recursion Example 2
+
+    // int n;
+    // printf("\n\tInput a to find its factorial : ");
+    // scanf("%d", &n);
+    // printf("\n\n\tFactorial for the given number is : ");
+    // cout << factorial(n);
+
+
+    // Recursion Example 3 : Finding n'th term of Fibonacci number
+
+    int n;
+    cout << "Enter the number : ";
+    cin >> n;
+    printf("\n\nThe term in fibonacci sequence at position ");
+    cout << n;
+    printf(" is ");
+    cout << fib(n);
+    return 0;
+
+}