Why elif with multiple conditions not working

Maruf Talukdar 0
Viewed 16

I'm trying to solve the firstNotRepeatingCharacter question on CodeSignal. The problem is that given a string of characters (in this case s), I need to return the first non-duplicate character. I don't understand why my code isn't working.

I'll paste the link to the problem although you'll probably need to sign up.

def solution(s):
    
    # run through all elements
    
    for i,el in enumerate(s):
        
        # helps check what's going on
        #print(i,el,s[i+1:], s[i-1::-1])
        
        # if it's the first element, only check for duplicates in characters in front of it
        # if no duplicate present, return first element
        if i == 0:
            if el not in s[i+1:]:
                return i,el
            
        # if it's not the first element, check for duplicates in characters in front of it and behind it
        # if no duplicate is present, return that element
        elif el not in ( s[i+1:] or s[i-1::-1] ):
            return i,el
        
        
    #otherwise, return '_'    
    return '_'
        
    s='habahzb'
    solution(s)

expected output z, output a

I have tried:

elif (el not in s[i+1:]) or (el not in s[i-1::-1]):

But I run into a similar issue.

python-3.x
1 Answers

You have written your test incorrectly:

el not in ( s[i+1:] or s[i-1::-1] )

It should be

el not in s[i+1:] and el not in s[:i-1]

The condition you have basically translates to

el not in s[i+1:]

because s[i+1:] is a string of non-zero length and thus "truthy" so the rest of the expression is ignored (but was the wrong way of writing it anyway).

usergAKD0
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