longest palindrome in Ruby on Rails -
write method takes in string of lowercase letters (no uppercase letters, no repeats). consider substrings of string: consecutive sequences of letters contained inside string. find longest such string of letters palindrome.
based on local method palindrome?(string), implemented longest-palindrome(string) below test cases:
def palindrome?(string) = 0 while < string.length if string[i] != string[(string.length - 1) - i] return false end += 1 end return true end def longest_palindrome(string) dix = 0 lstr = "" lstrc = nil while dix < string.length dix2 = 1 while dix2 < string.length str = string.slice(dix,dix2) count = str.length if palindrome?(str) if lstrc == nil || lstrc < count lstr = str lstrc = count end end dix2 += 1 end dix += 1 end puts(lstr) return lstr end # these tests check code working. after writing # solution, should print true. puts( 'longest_palindrome("abcbd") == "bcb": ' + (longest_palindrome('abcbd') == 'bcb').to_s ) puts( 'longest_palindrome("abba") == "abba": ' + (longest_palindrome('abba') == 'abba').to_s ) puts( 'longest_palindrome("abcbdeffe") == "effe": ' + (longest_palindrome('abcbdeffe') == 'effe').to_s ) test results below:
bcb longest_palindrome("abcbd") == "bcb": true bb longest_palindrome("abba") == "abba": false effe longest_palindrome("abcbdeffe") == "effe": true why did second test failed?
... line preventing considering entire string
while dix2 < string.length so when dix whole string, you're not doing testing palindromes
change line to...
while dix2 <= string.length it more efficient if did...
while dix2 <= string.length - dix which prevent testing (for, say, string of length 10), string(7,3) , string(7,4) , string(7,5) etc. etc., same string.
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