refactor 234

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_234.java

@@ -80,4 +80,24 @@ public boolean isPalindrome(ListNode head) {
         }
     }
 
+    public static class Solution3 {
+        /**
+         * O(n) time
+         * O(n) space
+         */
+        public boolean isPalindrome(ListNode head) {
+            List<Integer> list = new ArrayList<>();
+            while (head != null) {
+                list.add(head.val);
+                head = head.next;
+            }
+            for (int i = 0, j = list.size() - 1; i <= j; i++, j--) {
+                if (list.get(i) != list.get(j)) {
+                    return false;
+                }
+            }
+            return true;
+        }
+    }
+
 }