Add longest-palindromic-substring solution

Author: Jeehay28

longest-palindromic-substring/Jeehay28.js

@@ -0,0 +1,76 @@
+// ✅ Time Complexity: O(n^2), where n represents the length of the input string s
+// ✅ Space Complexity: O(n)
+
+/**
+ * @param {string} s
+ * @return {string}
+ */
+var longestPalindrome = function (s) {
+  let max_left = 0,
+    max_right = 0;
+
+  for (let i = 0; i < s.length; i++) {
+    // Odd-length palindromes
+    let left = i,
+      right = i;
+
+    while (left >= 0 && right < s.length && s[left] === s[right]) {
+      if (max_right - max_left < right - left) {
+        max_right = right;
+        max_left = left;
+      }
+      left -= 1;
+      right += 1;
+    }
+
+    // Even-length palindromes
+    left = i;
+    right = i + 1;
+
+    while (left >= 0 && right < s.length && s[left] === s[right]) {
+      if (max_right - max_left < right - left) {
+        max_right = right;
+        max_left = left;
+      }
+      left -= 1;
+      right += 1;
+    }
+  }
+
+  return s.slice(max_left, max_right + 1);
+};
+
+// ✅ Time Complexity: O(n^3), where n represents the length of the input string s
+// ✅ Space Complexity: O(n)
+
+/**
+ * @param {string} s
+ * @return {string}
+ */
+// var longestPalindrome = function (s) {
+//   const isPalindromic = (left, right) => {
+//     while (left < right) {
+//       if (s[left] !== s[right]) {
+//         return false;
+//       }
+//       left += 1;
+//       right -= 1;
+//     }
+
+//     return true;
+//   };
+
+//   let max_left = 0,
+//     max_right = 0;
+//   for (let l = 0; l < s.length; l++) {
+//     for (let r = 0; r < s.length; r++) {
+//       if (isPalindromic(l, r) && max_right - max_left < r - l) {
+//         max_left = l;
+//         max_right = r;
+//       }
+//     }
+//   }
+
+//   return s.slice(max_left, max_right + 1);
+// };
+