Question

How to find longest palindrome substring in Pascal

Answer 1

program LongestPalindrome;

function IsPalindrome(const s: string; i, j: Integer): Boolean;
var
  k: Integer;
begin
  for k := 0 to (j - i) div 2 do
    if s[i + k] <> s[j - k] then
    begin
      IsPalindrome := False;
      Exit;
    end;
  IsPalindrome := True;
end;

function LongestPalindromeSubstring(const s: string): Integer;
var
  i, j, k, len, start, longestLength: Integer;
begin
  len := Length(s);
  longestLength := 1;
  start := 1;

  for i := 1 to len do
    for j := i to len do
      if IsPalindrome(s, i, j) and ((j - i + 1) > longestLength) then
      begin
        start := i;
        longestLength := j - i + 1;
      end;

  Write('Longest palindrome substring = ');
  for k := start to start + longestLength - 1 do
    Write(s[k]);
  Writeln;

  LongestPalindromeSubstring := longestLength;
end;

var
  input: string;
  lengthFound: Integer;
begin
  input := 'qabcbaproggorpxyyxzv';
  
  lengthFound := LongestPalindromeSubstring(input);
  Writeln('Length palindrome substring length = ', lengthFound);
end.




(*
run:

Longest palindrome substring = proggorp
Length palindrome substring length = 8

*)

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