isPalindrome 递归字符串

Question

why does this not work? It works for False palindrome; however, for anything True it never returns True.. I don't understand why this function does not return True? And how I should improve this same answer so that it returns True.

My logic was that after the function completes iterating through the entire string, it will return True.

def isPalindrome(string, i = 0):
    if i == len(string): 
        return True
    if string[i] != string[len(string)-1-i]:
        return False
    isPalindrome(string,i+1)

Answer 1

Problem is with your last line:

isPalindrome(string,i+1)

That last line will eventually resolve to either True or False -- but how is that value being returned? (It isn't.)

Try:

return isPalindrome(string,i+1)

Answer 2

Check out the visualization here

My hint would be check what you are returning (ie what does isPalindrome return).

If you want just the answer, it is here