When should we use recursion and when should we avoid it?

Recursion is less efficient than a loop. Therefore use a loop instead of recursion whenever you can. Recursion usually helps create cleaner code. Therefore use recursion when clarity is needed more than efficiency. Consider the following example, which calculates the n^th term in the Fibbonacci series. The recursive function calls itself 21,890 times to calculate the 20^th term whereas the non-recursive function goes through the loop only 19 times.

Using recursion:

int fibbo ( int n )

{

if ( n < 2 )

return ( n ) ;

return ( fibbo ( n – 1 ) + fibbo ( n ) ) ;

}

Without recursion:

int fibbo ( int n )

{

int a = 0, b = 1, c ;

if ( n < 2 )

return ( n ) ;

while ( 2 <= n– )

{

c = a + b ;

a = b ;

b = c ;

}

return ( c ) ;

}