feat: longest-palindromic-substring

Author: minji-go

longest-palindromic-substring/minji-go.java

@@ -0,0 +1,36 @@
+/**
+ * <a href="https://leetcode.com/problems/longest-palindromic-substring/">week15-3. longest-palindromic-substring</a>
+ * <li>Description: Given a string s, return the longest palindromic substring in s</li>
+ * <li>Topics: Two Pointers, String, Dynamic Programming</li>
+ * <li>Time Complexity: O(N), Runtime 15ms   </li>
+ * <li>Space Complexity: O(N), Memory 42.13MB</li>
+ */
+
+class Solution {
+    public String longestPalindrome(String s) {
+        int start = 0;
+        int maxLength = 1;
+
+        for (int i = 0; i < s.length(); i++) {
+            int len1 = findPalindrome(s, i, i);
+            int len2 = findPalindrome(s, i, i + 1);
+
+            int len = Math.max(len1, len2);
+            if (len > maxLength) {
+                maxLength = len;
+                start = i - (len - 1) / 2;
+            }
+        }
+
+        return s.substring(start, start + maxLength);
+    }
+
+    public int findPalindrome(String s, int left, int right) {
+        while (left >= 0 && right < s.length() && s.charAt(left) == s.charAt(right)) {
+            left--;
+            right++;
+        }
+
+        return right - left - 1;
+    }
+}