【LeetCode】145. 二叉树的后序遍历（递归法）（错题2刷）

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */

func postOrder(root *TreeNode, order *[]int) {
    if root == nil {
        return
    }
    // 左
    postOrder(root.Left, order)
    // 右
    postOrder(root.Right, order)
    // 中
    *order = append(*order, root.Val)
}

func postorderTraversal(root *TreeNode) []int {
    res := []int{}
    postOrder(root, &res)
    return res
}