longestpalindromeinstring.js

function longestPalindrome(str) {
  let longestPalindrome = "";
  
  for (let i = 0; i < str.length; i++) {
    // Check for odd-length palindrome
    let left = i;
    let right = i;
    while (left >= 0 && right < str.length && str[left] === str[right]) {
      let palindrome = str.slice(left, right + 1);
      if (palindrome.length > longestPalindrome.length) {
        longestPalindrome = palindrome;
      }
      left--;
      right++;
    }
    
    // Check for even-length palindrome
    left = i;
    right = i + 1;
    while (left >= 0 && right < str.length && str[left] === str[right]) {
      let palindrome = str.slice(left, right + 1);
      if (palindrome.length > longestPalindrome.length) {
        longestPalindrome = palindrome;
      }
      left--;
      right++;
    }
  }
  
  return longestPalindrome;
}

// Example usage:
console.log(longestPalindrome("babad")); // "bab" or "aba"
console.log(longestPalindrome("cbbd")); // "bb"