Recursion

What is Recursion?

            A function calls itself is called recursion. Recursion is a useful technique. it is shorter and easier to write.

Example:

Factorial problems using Recursion.

      Java

1. int fact(int n){
2.      if(n==1)
3.         return 1;
4.      else if(n==0)
5.         return 1;
6.      else return n*fact(n-1)
7. }
8. fact(5)

     Python

1. def fact(n):
2.       if n==0:
3.           return 1
4.       return n*fact(n-1)
5. print(fact(5))

    

Explanation:

       

           5*fact(5-1)                   5*return value 24= 120 final result 

                4*fact(4-1)              4*return value 6  = 24

                    3*fact(3-1)          3*return value 2  = 6

                        2*fact(2-1)      2*return value 1  = 2

                           1*fact(1-1)    return 1

Each recursive call makes a new copy of that method in memory. Memory removed for that method once it return.