leetcode 94. 二叉树的中序遍历

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]

 1 //迭代算法
 2 class Solution {
 3     public List<Integer> inorderTraversal(TreeNode root) {
 4         List<Integer> list = new ArrayList<Integer>();
 5         if(root==null)return list;
 6         Stack<TreeNode> stack = new Stack<TreeNode>();
 7         stack.push(root);
 8         TreeNode cur = root.left;
 9         while(cur!=null||!stack.empty()){
10             while(cur!=null){
11                 stack.push(cur);
12                 cur=cur.left;
13             }
14             TreeNode tmpnode = stack.pop();
15             list.add(tmpnode.val);
16             cur = tmpnode.right;
17         }
18         return list;
19     }
20 }
21 
22 
23  //递归算法
24 class Solution {
25     public List<Integer> inorderTraversal(TreeNode root) {
26         List<Integer> list = new ArrayList<Integer>();
27         if(root==null)return list;
28         inorder(root,list);
29         return list;
30     }
31     public void inorder(TreeNode node,List<Integer> list){
32         if(node.left!=null)inorder(node.left,list);
33         list.add(node.val);
34         if(node.right!=null)inorder(node.right,list);
35     }
36 }