题解 | #二叉树的后序遍历#

import java.util.*;
//跟前序中序差不多，方法名以及顺序换一下就可以了
public class Solution {

    List<Integer> list = new ArrayList<>();
    public int[] postorderTraversal (TreeNode root) {
        list = postOrder(root);
        int[] res = new int[list.size()];
        for (int i = 0; i < list.size(); i++) {
            res[i] = list.get(i);
        }
        return res;
    }
    public List<Integer> postOrder(TreeNode root) {
        if (root == null) return list;
        postOrder(root.left);
        postOrder(root.right);
        list.add(root.val);
        return list;
    }
}