Add solution 094

Author: yanglbme

README.md

@@ -48,6 +48,7 @@ Complete solutions to Leetcode problems, updated daily.
 | 063 | [Unique Paths II](https://github.com/yanglbme/leetcode/tree/master/solution/063.Unique%20Paths%20II) | `Array`, `Dynamic Programming` |
 | 075 | [Sort Colors](https://github.com/yanglbme/leetcode/tree/master/solution/075.Sort%20Colors) | `Array`, `Two Pointers`, `Sort` |
 | 082 | [Remove Duplicates from Sorted List II](https://github.com/yanglbme/leetcode/tree/master/solution/082.Remove%20Duplicates%20from%20Sorted%20List%20II) | `Linked List` |
+| 094 | [Binary Tree Inorder Traversal](https://github.com/yanglbme/leetcode/tree/master/solution/094.Binary%20Tree%20Inorder%20Traversal) | `Hash Table`, `Stack`, `Tree` |
 | 153 | [Find Minimum in Rotated Sorted Array](https://github.com/yanglbme/leetcode/tree/master/solution/153.Find%20Minimum%20in%20Rotated%20Sorted%20Array) | `Array`, `Binary Search` |
 
 

solution/094.Binary Tree Inorder Traversal/README.md

@@ -0,0 +1,53 @@
+## 二叉树的中序遍历
+### 题目描述
+
+给定一个二叉树，返回它的中序 遍历。
+
+示例:
+```
+输入: [1,null,2,3]
+   1
+    \
+     2
+    /
+   3
+
+输出: [1,3,2]
+```
+
+进阶: 递归算法很简单，你可以通过迭代算法完成吗？
+
+### 解法
+递归算法，先递归左子树，再访问根结点，最后递归右子树。
+
+- 递归算法
+
+```java
+
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public List<Integer> inorderTraversal(TreeNode root) {
+        List<Integer> list = new ArrayList<>();
+        inorderTraversal(root, list);
+        return list;
+    }
+    
+    private void inorderTraversal(TreeNode root, List<Integer> list) {
+        if (root == null) {
+            return;
+        }
+        inorderTraversal(root.left, list);
+        list.add(root.val);
+        inorderTraversal(root.right, list);
+    }
+    
+}
+```

solution/094.Binary Tree Inorder Traversal/Solution.java

@@ -0,0 +1,17 @@
+class Solution {
+    public List<Integer> inorderTraversal(TreeNode root) {
+        List<Integer> list = new ArrayList<>();
+        inorderTraversal(root, list);
+        return list;
+    }
+    
+    private void inorderTraversal(TreeNode root, List<Integer> list) {
+        if (root == null) {
+            return;
+        }
+        inorderTraversal(root.left, list);
+        list.add(root.val);
+        inorderTraversal(root.right, list);
+    }
+    
+}