Add week 10 solutions: longestPalindromicSubstring

Author: yolophg

longest-palindromic-substring/yolophg.js

@@ -0,0 +1,31 @@
+// Time Complexity: O(n^2)
+// Space Complexity: O(1)
+
+var longestPalindrome = function (s) {
+  let start = 0,
+    maxLength = 1;
+
+  // to expand around the center and update the start and maxLength
+  function expandAroundCenter(left, right) {
+    while (left >= 0 && right < s.length && s[left] === s[right]) {
+      left--;
+      right++;
+    }
+    // update the start and maxLength if a longer palindrome is found
+    if (maxLength < right - left - 1) {
+      start = left + 1;
+      maxLength = right - left - 1;
+    }
+  }
+
+  // iterate through each character in the string
+  for (let i = 0; i < s.length; i++) {
+    // expand around the current character
+    expandAroundCenter(i, i);
+    // expand around the current and next character
+    expandAroundCenter(i, i + 1);
+  }
+
+  // return the longest palindromic substring
+  return s.substring(start, start + maxLength);
+};