JavaScript-Course/Strings.html at main · Dhanushpolagani/JavaScript-Course · GitHub

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<!DOCTYPE html>
<html>
<head>
  <title>Longest Palindromic Substring</title>
</head>
<body>
  <h2>Find Longest Palindromic Substring</h2>

  <input type="text" id="inputString" placeholder="Enter a string">
  <button onclick="handleFindPalindrome()">Find Longest Palindrome</button>

  <p><strong>Longest Palindromic Substring:</strong> <span id="result"></span></p>

  <script>
    function findLongestPalindrome(str) {
      if (!str || str.length < 1) return "";
      let start = 0, end = 0;

      for (let i = 0; i < str.length; i++) {
        let len1 = expandFromCenter(str, i, i);
        let len2 = expandFromCenter(str, i, i + 1);
        let len = Math.max(len1, len2);

        if (len > end - start) {
          start = i - Math.floor((len - 1) / 2);
          end = i + Math.floor(len / 2);
        }
      }

      return str.substring(start, end + 1);
    }

    function expandFromCenter(s, left, right) {
      while (left >= 0 && right < s.length && s[left] === s[right]) {
        left--;
        right++;
      }
      return right - left - 1;
    }

    function handleFindPalindrome() {
      const input = document.getElementById('inputString').value;
      const result = findLongestPalindrome(input);
      document.getElementById('result').innerText = result;
    }
  </script>
</body>
</html>