145. Binary Tree Postorder Traversal.go

package leetcode

import (
	"github.com/halfrost/LeetCode-Go/structures"
)

// TreeNode define
type TreeNode = structures.TreeNode

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

func postorderTraversal(root *TreeNode) []int {
	var result []int
	postorder(root, &result)
	return result
}

func postorder(root *TreeNode, output *[]int) {
	if root != nil {
		postorder(root.Left, output)
		postorder(root.Right, output)
		*output = append(*output, root.Val)
	}
}