Recursion

Recursion

è      When any called function in turn calls  another function a process of chaining occurs.

è      When function calls itself the process is known as recursion.Recursion is a special case of this process , where a function calls itself.

Ex,

          void main()

                   {

                             printf(“\n This is recursive main()”);

                             main();

                   }

Here the main() calls itself and the message written in printf() will display. Execution is terminated abruptly ; otherwise the execution will continue indefinitely.

The calculation of factorial of given number can be easily find out using recursion. Factorial of a number n is expressed as a series of repetitive multiplication as shown below.

Factorial of 5 =5*4*3*2*1

                    = 120

Ex

#include<stdio.h>

#include<conio.h>

int fact(int);

void main()

 {

    int n,f;

    clrscr();

    printf("\n Enter any number : ");

    scanf("%d",&n);

    f=fact(n);

    printf("\n Factorial of %d = %d",n,f);

    getch();

 }

int fact(int n)

 {

    if(n==1)

      {

          return(1);

      }

    else

      {

          return(n*fact(n-1));

      }

 }

The execution of recursion is as follw:

Suppose n=5 then,

First checks    if(n==1)  since the value of n in not 1 , the statement

return(n*fact(n-1)); will execute as :

 

return(5*fact(4));     5*24  =120

return(4*fact(3));     4*6   =24

return(3*fact(2));     3*2   =6

return(2*fact(1));     2*1   =2

          When n=1 then returns 1 to the last call of function.

Posted By : Ruchita Pandya