print 0 if the word is palindrome and -1 if it is not(without conditions and loops)

Question

I need to check whether the string is a palindrome or not (without conditions and loops) and print '0' if the string is palindrome and '-1' if it is not a palindrome.

I am unsure what to do after reversing the string by string[::-1]. How to compare both strings to check palindrome without any loops or conditions?

(PS. I am not supposed to use any loops or conditions(including if,else))

Answer 1

As you asked for an explanation, I am writing an answer for you.

But be aware, except in very particular cases (such as golf code), I strongly discourage this practice.

If you want to not use if else, you could simply "trick it", using the fact that True converts to 1 implicitly and False to 0 in some cases.

You can use it in two ways :

Solution 1

Access elements in an array converts the bool to int, let's construct an array with the right element at the right index :

[-1,0][string==string[::-1]]

If string==string[::-1] evaluates to True (this is a palyndrome) then the second element of the array will be accessed. Otherwise, the first one.

Solution 2

Another solution, is to find a "function" which converts 1 to 0, and 0 to -1. The easy one is f(x) = x - 1

Which leads to :

(string == string[::-1]) - 1

Keep in mind, my comment was more a joke than a real solution, you should probably not use it in the real world !

PS: By "no conditions", I suspect it to mean "without comparing letters one by one", but I do think a

if string == string[::-1]:
    print(0)
else:
    print(-1)

is totally acceptable.