This interview question requires you to reverse a string using recursion. Make sure to think of the base case here.

Again, make sure you use recursion to accomplish this. Do not slice (e.g. string[::-1]) or use iteration, there must be a recursive call for the function.

Solution

def reverse(s):
    if(len(s)<=1):
        return s
    else:
        m = int(len(s)/2)
        return reverse(s[m:]) + (reverse((s[:m])))
    pass

reverse('hello world')

‘dlrow olleh’

Test Your Solution

Run the cell below to test your solution against the following cases:

string = 'hello'
string = 'hello world'
string = '123456789'

'''
RUN THIS CELL TO TEST YOUR FUNCTION AGAINST SOME TEST CASES
'''

from nose.tools import assert_equal

class TestReverse(object):
    
    def test_rev(self,solution):
        assert_equal(solution('hello'),'olleh')
        assert_equal(solution('hello world'),'dlrow olleh')
        assert_equal(solution('123456789'),'987654321')
        
        print ('PASSED ALL TEST CASES!')
        
# Run Tests
test = TestReverse()
test.test_rev(reverse)

PASSED ALL TEST CASES!

Recommended: Introduction to Recursion

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Hassan Raza