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I am looking for the longest common prefix and my code isnt working as I would like it to. It can detect prefix in every list below (list one to seven, except four):

four = ["a", "a", "b"]

there is no common prefix but my program returns "a". I need to get "". How can I fix this, please? (I'm learning to code :-))

My code:

one = ["aac", "aab", "aabb"] #aa
two = ["a", "a"] #a
three = ["a"] #a
four = ["a", "a", "b"] #is "" but i get "a"
five = ["aaaa", "bbb", "ccc"] #""
six = ["marmelada", "marketa", "marek"] #mar
seven = ["", "", ""] #""

def check_prefix(words):
    
    for i in range(1, len(words[0])+1):
        if len(words) == 1:
            return words[0]
        for j in words[1:]: 
            if i == len(words[0]) and words[0][:i] == j[:i]:
                return words[0][:i]
            if words[0][:i] != j[:i]:
                return words[0][:i-1]
            
    return ""


print(check_prefix(one))
print(check_prefix(two))
print(check_prefix(three))
print(check_prefix(four))
print(check_prefix(five))
print(check_prefix(six))
print(check_prefix(seven))

I trid to use module os as os.path.commonprefix() and this worked well for me. However I would like to fix my code.

xSilence8x
  • 1
  • Basically the first "return" in the inner for-loop is too early before you looked at all words and (from the outer for-loop) all characters of `words[0]`. – Michael Butscher Jan 01 '23 at 11:50

0 Answers0