Create LongestPalindromicSubstring.java

Author: Foxeyyy

LongestPalindromicSubstring.java

@@ -0,0 +1,42 @@
+class Solution {
+
+    //Time: O(n^2), where n is s length
+    //Space: O(1)
+    public String longestPalindrome(String s) {
+        
+        String longestPal = "";
+        
+        for(int i = 0; i < s.length(); i++) {
+            int offset1 = expandOffset(s, i, i);
+            int offset2 = expandOffset(s, i, i + 1);
+            
+            String subs = "";
+            
+            int maxOffset = Math.max(offset1, offset2);
+            
+            if (offset2 > offset1) {
+                subs = s.substring(i - maxOffset + 1, i + maxOffset + 1);
+            } else {
+                subs = s.substring(i - maxOffset, i + maxOffset + 1);   
+            }
+
+            if (longestPal.length() < subs.length()) longestPal = subs;
+            
+        }
+        
+        return longestPal;
+        
+    }
+    
+    private int expandOffset(String s, int left, int right) {
+        
+        while(left >= 0 && right < s.length() && s.charAt(left) == s.charAt(right)) {
+            left--;
+            right++;
+        }
+        
+        return (right - left - 1) / 2;
+        
+    }
+
+}