Recursion

Any questions before we start?

Recursion Basics

Recursion

Recursion is the process of defining a problem (or the solution to a problem) in terms of (a simpler version of) itself.

Example

we can define the operation "Go to Home" as:

Base Case

1. If you are at home, stop moving.

Recursive Case

2. Take one step toward home.

3. "Go To Home".

Code

Text


//A Simple Recursive Function 
static void goHome(x,Home){

  if(x == Home){
      print("Reached Home")
      return;
  }

  x = x + 1
  goHome(x,Home) 
}


//Main
int x = 1
int Home = 10
goHome(x,Home);

Recursion = Principal of Mathematical Induction

1. Figure of the Smallest Case

2. Always Assume the Subproblem Can be Solved

3. Solve the current problem assuming subproblem solution exists

Factorial of Number

Input

Output

120

Call Stack! 👨‍💻

Time & Space Utilisation 👨‍💻

Increasing Numbers

Given N, print numbers from 1 to N without using a Loop (Use Recursion)

Input

Output

1, 2, 3, 4, 5

Decreasing Numbers

Given N, print numbers from 1 to N without using a Loop (Use Recursion)

Input

Output

5, 4, 3, 2, 1

Sum the Digits

Given N, print the sum of digits of that number using recursion.

Input

512

Output