0094. Binary Tree Inorder Traversal

Author: coderbean

docs/_sidebar.md

@@ -67,4 +67,5 @@
 * [0091. Decode Ways](markdown/0091.%20Decode%20Ways)
 * [0092. Reverse Linked List II](markdown/0092.%20Reverse%20Linked%20List%20II)
 * [0093. Restore IP Addresses](markdown/0093.%20Restore%20IP%20Addresses)
+* [0094. Binary Tree Inorder Traversal](markdown/0094.%20Binary%20Tree%20Inorder%20Traversal)
 * [0146. LRU Cache](markdown/0146.%20LRU%20Cache)

docs/markdown/0094. Binary Tree Inorder Traversal.md

@@ -0,0 +1,61 @@
+### [94\. Binary Tree Inorder Traversal](https://leetcode.com/problems/binary-tree-inorder-traversal/)
+
+Difficulty: **Medium**
+
+
+Given a binary tree, return the _inorder_ traversal of its nodes' values.
+
+**Example:**
+
+```
+Input: [1,null,2,3]
+   1
+    \
+     2
+    /
+   3
+
+Output: [1,3,2]
+```
+
+**Follow up:** Recursive solution is trivial, could you do it iteratively?
+
+
+#### Solution
+
+Language: **Java**
+
+```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) {
+        Stack<TreeNode> stack = new Stack<>();
+        List<Integer> result = new ArrayList<>();
+​
+        TreeNode p = root;
+        while (p != null || !stack.isEmpty()) {
+            // 一直向左，把所有节点压栈
+            while (p != null) {
+                stack.push(p);
+                p = p.left;
+            }
+            // 压栈结束，元素出栈
+            p = stack.pop();
+            // 打印 value
+            result.add(p.val);
+            // 对右子树做同样的操作
+            p = p.right;
+        }
+        return result;
+    }
+}
+```
+![LH5Tf6](https://cdn.jsdelivr.net/gh/PicGoBed/PicBed@master/uPic/LH5Tf6.png)

src/main/java/leetcode/_94_/Main.java

@@ -0,0 +1,20 @@
+package leetcode._94_;
+
+import leetcode.common.TreeNode;
+
+/**
+ * Created by zhangbo54 on 2019-03-04.
+ */
+public class Main {
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+
+        TreeNode root = new TreeNode(1);
+        TreeNode n2 = new TreeNode(2);
+        TreeNode n3 = new TreeNode(3);
+        root.right = n2;
+        n2.left = n3;
+        System.out.println(solution.inorderTraversal(root));
+    }
+}
+

src/main/java/leetcode/_94_/Solution.java

@@ -0,0 +1,30 @@
+package leetcode._94_;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Stack;
+
+import leetcode.common.TreeNode;
+
+class Solution {
+    public List<Integer> inorderTraversal(TreeNode root) {
+        Stack<TreeNode> stack = new Stack<>();
+        List<Integer> result = new ArrayList<>();
+
+        TreeNode p = root;
+        while (p != null || !stack.isEmpty()) {
+            // 一直向左，把所有节点压栈
+            while (p != null) {
+                stack.push(p);
+                p = p.left;
+            }
+            // 压栈结束，元素出栈
+            p = stack.pop();
+            // 打印 value
+            result.add(p.val);
+            // 对右子树做同样的操作
+            p = p.right;
+        }
+        return result;
+    }
+}

src/main/java/leetcode/_94_/solution.md

@@ -0,0 +1,61 @@
+### [94\. Binary Tree Inorder Traversal](https://leetcode.com/problems/binary-tree-inorder-traversal/)
+
+Difficulty: **Medium**
+
+
+Given a binary tree, return the _inorder_ traversal of its nodes' values.
+
+**Example:**
+
+```
+Input: [1,null,2,3]
+   1
+    \
+     2
+    /
+   3
+
+Output: [1,3,2]
+```
+
+**Follow up:** Recursive solution is trivial, could you do it iteratively?
+
+
+#### Solution
+
+Language: **Java**
+
+```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) {
+        Stack<TreeNode> stack = new Stack<>();
+        List<Integer> result = new ArrayList<>();
+​
+        TreeNode p = root;
+        while (p != null || !stack.isEmpty()) {
+            // 一直向左，把所有节点压栈
+            while (p != null) {
+                stack.push(p);
+                p = p.left;
+            }
+            // 压栈结束，元素出栈
+            p = stack.pop();
+            // 打印 value
+            result.add(p.val);
+            // 对右子树做同样的操作
+            p = p.right;
+        }
+        return result;
+    }
+}
+```
+![LH5Tf6](https://cdn.jsdelivr.net/gh/PicGoBed/PicBed@master/uPic/LH5Tf6.png)

src/main/java/leetcode/common/TreeNode.java

@@ -0,0 +1,12 @@
+package leetcode.common;
+
+/**
+ * Created by jacob on 2020/2/29.
+ */
+public class TreeNode {
+    public int val;
+    public TreeNode left;
+    public TreeNode right;
+
+    public TreeNode(int x) { val = x; }
+}