Find the Longest Palindromic Substring?

(Repeated here for convenience)

string LongestPalindrome(string s)

if (string.IsNullOrEmpty(s)) return "";

int start = 0, maxLen = 1;

for (int i = 0; i < s.Length; i++)

ExpandAroundCenter(s, i, i, ref start, ref maxLen);

ExpandAroundCenter(s, i, i + 1, ref start, ref maxLen);

return s.Substring(start, maxLen);

void ExpandAroundCenter(string s, int left, int right, ref int

start, ref int maxLen)

while (left >= 0 && right < s.Length && s[left] == s[right])

Follow on:

if (right - left + 1 > maxLen)

start = left;

maxLen = right - left + 1;

left--;

right++;