[N-0] refactor 156

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_156.java

@@ -3,6 +3,8 @@
 import com.fishercoder.common.classes.TreeNode;
 
 /**
+ * 156. Binary Tree Upside Down
+ *
  * Given a binary tree where all the right nodes are either leaf nodes with a sibling
  * (a left node that shares the same parent node) or empty,
  * flip it upside down and turn it into a tree where the original right nodes turned into left leaf nodes. Return the new root.
@@ -14,25 +16,29 @@
   2  3
  / \
 4   5
+
  return the root of the binary tree [4,5,2,#,#,3,1].
     4
    / \
   5  2
     / \
    3  1
+
  confused what "{1,#,2,3}" means? > read more on how binary tree is serialized on OJ.
  */
 public class _156 {
 
-    public TreeNode upsideDownBinaryTree(TreeNode root) {
-        if (root == null || root.left == null && root.right == null) {
-            return root;
+    public static class Solution1 {
+        public TreeNode upsideDownBinaryTree(TreeNode root) {
+            if (root == null || root.left == null && root.right == null) {
+                return root;
+            }
+            TreeNode newRoot = upsideDownBinaryTree(root.left);
+            root.left.left = root.right;
+            root.left.right = root;
+            root.left = null;
+            root.right = null;
+            return newRoot;
         }
-        TreeNode newRoot = upsideDownBinaryTree(root.left);
-        root.left.left = root.right;
-        root.left.right = root;
-        root.left = null;
-        root.right = null;
-        return newRoot;
     }
 }

src/test/java/com/fishercoder/_156Test.java

@@ -0,0 +1,30 @@
+package com.fishercoder;
+
+import com.fishercoder.common.classes.TreeNode;
+import com.fishercoder.common.utils.TreeUtils;
+import com.fishercoder.solutions._156;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.Arrays;
+
+import static org.junit.Assert.assertEquals;
+
+public class _156Test {
+    private static _156.Solution1 solution1;
+    private static TreeNode root;
+    private static TreeNode expected;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _156.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        root = TreeUtils.constructBinaryTree(Arrays.asList(1, 2, 3, 4, 5));
+        expected = TreeUtils.constructBinaryTree(Arrays.asList(4, 5, 2, null, null, 3, 1));
+        assertEquals(expected, solution1.upsideDownBinaryTree(root));
+    }
+
+}