refactor 206

fishercoder1534 · fishercoder1534 · commit 9e718d1235d3 · 2020-01-13T11:46:02.000-08:00
diff --git a/src/main/java/com/fishercoder/solutions/_206.java b/src/main/java/com/fishercoder/solutions/_206.java
@@ -17,28 +17,16 @@
 public class _206 {
 
     public static class Solution1 {
-        /**
-         * creating a newHead = null is a very common/smart way to handle such cases, the logic flows out very naturally:
-         * create a new node called "next" to hold current head's next node
-         * then we could redirect head's next pointer to point to newHead which is head's previous node
-         * the above two steps finished the reversion, to continue this process until we reach the end of the original list,
-         * we'll assign current "head" to new "newHead", and current "next" to be new "head" for the next iteration, here's the code
-         */
         public ListNode reverseList(ListNode head) {
-            /**It works out the best to set up a debug point and visualize this process:
-             * e.g. 1->2->3-null
-             * at the end of the first iteration of the while loop, the status is like this:
-             * newHead: 1->null
-             * head: 2->3-null
-             * then it continues the iteration.*/
-            ListNode newHead = null;
-            while (head != null) {
-                ListNode next = head.next;
-                head.next = newHead;
-                newHead = head;
-                head = next;
+            ListNode prev = null;
+            ListNode curr = head;
+            while (curr != null) {
+                ListNode next = curr.next;
+                curr.next = prev;
+                prev = curr;
+                curr = next;
             }
-            return newHead;
+            return prev;
         }
     }
 
diff --git a/src/test/java/com/fishercoder/_206Test.java b/src/test/java/com/fishercoder/_206Test.java
@@ -21,10 +21,13 @@ public static void setup() {
 
     @Test
     public void test1() {
-        head = LinkedListUtils.contructLinkedList(new int[]{1, 2, 3});
-        assertEquals(LinkedListUtils.contructLinkedList(new int[]{3, 2, 1}), solution1.reverseList(head));
+        head = LinkedListUtils.contructLinkedList(new int[]{1, 2, 3, 4});
+        assertEquals(LinkedListUtils.contructLinkedList(new int[]{4, 3, 2, 1}), solution1.reverseList(head));
+    }
 
-        head = LinkedListUtils.contructLinkedList(new int[]{1, 2, 3});
-        assertEquals(LinkedListUtils.contructLinkedList(new int[]{3, 2, 1}), solution2.reverseList(head));
+    @Test
+    public void test2() {
+        head = LinkedListUtils.contructLinkedList(new int[]{1, 2, 3, 4});
+        assertEquals(LinkedListUtils.contructLinkedList(new int[]{4, 3, 2, 1}), solution2.reverseList(head));
     }
 }
