[N-0] refactor 108

Author: fishercoder1534

README.md

@@ -546,7 +546,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |111|[Minimum Depth of Binary Tree](https://leetcode.com/problems/minimum-depth-of-binary-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_111.java)| O(n)|O(1)~O(h) | Easy| BFS, DFS
 |110|[Balanced Binary Tree](https://leetcode.com/problems/balanced-binary-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_110.java)| O(n)|O(1)~O(h) | Easy| DFS
 |109|[Convert Sorted List to Binary Search Tree](https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_109.java)| O(n)|O(h) | Medium | DFS, Recursion
-|108|[Convert Sorted Array to Binary Search Tree](https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_108.java)| O(n)|O(h) | Medium| Tree
+|108|[Convert Sorted Array to Binary Search Tree](https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_108.java)| O(n)|O(h) | Easy | Tree
 |107|[Binary Tree Level Order Traversal II](https://leetcode.com/problems/binary-tree-level-order-traversal-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_107.java)| O(nlogn)|O(h) | Easy| BFS
 |106|[Construct Binary Tree from Inorder and Postorder Traversal](https://leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_106.java)| O(n)|O(n) | Medium| Recursion, Tree
 |105|[Construct Binary Tree from Preorder and Inorder Traversal](https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_105.java)| O(n)|O(n) | Medium| Recursion, Tree 

src/main/java/com/fishercoder/solutions/_108.java

@@ -9,19 +9,21 @@
  */
 public class _108 {
 
-    public TreeNode sortedArrayToBST(int[] num) {
-        return rec(num, 0, num.length - 1);
-    }
+    public static class Solution1 {
+        public TreeNode sortedArrayToBST(int[] num) {
+            return rec(num, 0, num.length - 1);
+        }
 
-    public TreeNode rec(int[] num, int low, int high) {
-        if (low > high) {
-            return null;
+        public TreeNode rec(int[] num, int low, int high) {
+            if (low > high) {
+                return null;
+            }
+            int mid = low + (high - low) / 2;
+            TreeNode root = new TreeNode(num[mid]);
+            root.left = rec(num, low, mid - 1);
+            root.right = rec(num, mid + 1, high);
+            return root;
         }
-        int mid = low + (high - low) / 2;
-        TreeNode root = new TreeNode(num[mid]);
-        root.left = rec(num, low, mid - 1);
-        root.right = rec(num, mid + 1, high);
-        return root;
     }
 
 }

src/test/java/com/fishercoder/_108Test.java

@@ -0,0 +1,23 @@
+package com.fishercoder;
+
+import com.fishercoder.common.utils.TreeUtils;
+import com.fishercoder.solutions._108;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class _108Test {
+    private static _108.Solution1 solution1;
+    private static int[] nums;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _108.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        nums = new int[]{1, 2, 3};
+        TreeUtils.printBinaryTree(solution1.sortedArrayToBST(nums));
+    }
+
+}