Longest palindromic substrings: Difference between revisions

=={{header|Nim}}==

Simple algorithm but working on Unicode code points.

<lang Nim>import sequtils, strutils, unicode

func isPalindrome(s: seq[Rune]): bool =

## Return true if a sequence of runes is a palindrome.

for i in 1..(s.len shr 1):

if s[i - 1] != s[^i]:

return false

result = true

func lps(s: string): seq[string] =

var maxLength = 0

var list: seq[seq[Rune]]

let r = s.toRunes

for first in 0..r.high:

for last in first..r.high:

let candidate = r[first..last]

if candidate.isPalindrome():

if candidate.len > maxLength:

list = @[candidate]

maxLength = candidate.len

elif candidate.len == maxLength:

list.add candidate

if maxLength > 1:

result = list.mapIt($it)

for str in ["babaccd", "rotator", "several", "palindrome", "piété", "tantôt", "étêté"]:

let result = lps(str)

if result.len == 0:

echo str, " → ", "<no palindromic substring of two of more letters found>"

else:

echo str, " → ", result.join(", ")</lang>

{{out}}

<pre>babaccd → bab, aba

rotator → rotator

several → eve

palindrome → <no palindromic substring of two of more letters found>

piété → été

tantôt → tôt

étêté → étêté</pre>