给定一个二叉树的根节点root
,返回它的中序遍历。
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public List<Integer> inorderTraversal(TreeNode root) {
List<Integer> a =new ArrayList<Integer>();
mediumOrder(root,a);
return a;
}
public void mediumOrder(TreeNode root,List<Integer> a){
if(root == null) return;
mediumOrder(root.left,a);
a.add(root.val);
mediumOrder(root.right,a);
}
}