问题描述
https://leetcode.com/problems/binary-tree-inorder-traversal/
代码
/**
* 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> res = new ArrayList<>();
helper(root, res);
return res;
}
public void helper(TreeNode root, List<Integer> res){
if(root != null){
if(root.left != null){
helper(root.left, res);
}
res.add(root.val);
if(root.right != null){
helper(root.right, res);
}
}
}
}
复杂度分析
- 时间复杂度：O(2^n)
- 空间复杂度：O(1)
