Longest palindrome in a substring of a string

Question

I'm trying to find the longest palindrome in a string and this is my take.

def palindrome(x):
    rev = x[::-1]
    a = False
    if (rev==x):
        a = True
    return a


def longest_palindrome(s):

    last = len(s) 
    lst = []
    for i in range (last):
        for j in range (i+1,last):
            b = s[i] + s[j]
            a = palindrome(b)
            if (a==True):
                lst.append(b)
            else:
                continue
    return lst

a = input("Enter the string: ")
longest_palindrome(a)

If my input is "aaba" it produces the output ['aa','aa','aa'] whereas the output should be ['aa', 'aba']. Is there a problem in the way I'm iterating?

Answer 1

I think the problem in your code is with finding the substrings. Try this

def palindrome(x):
    if len(x) <= 1: ## This condition checks if the length of the string is 1. And if so, it returns False
        return False
    return x == x[::-1]:


def longest_palindrome(s):

    last = len(s)
    lst = []
    for i in range(last):
        for j in range(i, last): ## Iterate from i to last not i+1 to last
            b = s[i:j+1]         ## Slicing the original string to get the substring and checking if it is a pallindrome or not.
            if palindrome(b):
                lst.append(b)
            else:
                continue
    return lst

a = input("Enter the string: ")
print(longest_palindrome(a))

. This code will help