How to create recursive function

Recursive function

Recursion is a way to call a function from inside its own declaration.

A recursive function usually consists of the following parts:

A base case when the function returns a value directly. A recursive case, which contains one or more recursive calls on smaller parts of the problem.

Compute the factorial of a number n. The factorial of n is defined as n x (n?1) x (n?2) x . . . x 1.

The mathematical definition of the factorial, which can be stated as follows:

• The factorial of 1 is 1.
• The factorial of a number n greater than 1 is the product of n and the factorial of n?1.

def factorial(n): 
    if n == 1: #   w ww  .  j  ava 2 s  .  co m
        return 1 
    else: 
        return n * factorial(n-1) 


print factorial(10);

The code above generates the following result.

Recursive search function

def search(sequence, number, lower, upper): 
    if lower == upper: 
        assert number == sequence[upper] 
        return upper 
    else: # w w  w . j  a  va2  s.co  m
        middle = (lower + upper) // 2 
        if number > sequence[middle]: 
            return search(sequence, number, middle+1, upper) 
        else: 
            return search(sequence, number, lower, middle) 


seq = [ 6,8, 7, 23, 100] 
seq.sort() 
print seq 
print search(seq, 4) 
print search(seq, 100)