Ruby longest palindrome - why does a slight modification in a while loop break my code? -


i'm trying solve ruby problem , can't figure out why having minor while loop difference renders 1 test false: longest_palindrome("abba") outputs "bb" instead of "abba", false. can solve , while loops, please no advanced methods. it's easier highlight difference in code block (first 1 working solution, second mine. assume palindrome? method defined): 

def longest_palindrome(string) best_palindrome = nil    idx1 = 0      ***while idx1 < string.length     length = 1     while (idx1 + length) <= string.length       substring = string.slice(idx1, length)***        if palindrome?(substring) && (best_palindrome == nil || substring.length > best_palindrome.length)         best_palindrome = substring       end        length += 1     end      idx1 += 1   end    return best_palindrome end   def longest_palindrome(string)   longest = nil    = 0   ***while < string.length     i2 = 1     while i2 < string.length***       if palindrome?(string.slice(i, i2)) == true && (longest == nil || string.slice(i, i2).length > longest.length)         longest = string.slice(i, i2)        end       i2 += 1     end     += 1   end    return longest end

this part of code...

while i2 < string.length

... means you're never checking maximum possible length.

"abba".slice(0,4) entire string, ever go "abba".slice(0,3) "abb".

so never test entire string.

change line to...

 while i2 <= string.length

...and should ok.


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