题解 | #实现二叉树先序，中序和后序遍历#

package main

import . "nc_tools"

func threeOrders(root *TreeNode) [][]int {
	// write code here
	res := make([][]int, 3)
	for i := 0; i < 3; i++ {
		res[i] = make([]int, 1010)
	}
	len := preOrder(root, res[0], 0)
	res[0] = res[0][0:len]
	len = midOrder(root, res[1], 0)
	res[1] = res[1][0:len]
	len = postOrder(root, res[2], 0)
	res[2] = res[2][0:len]
	return res
}

func postOrder(root *TreeNode, data []int, len int) int {
	if root == nil {
		return len
	}
	len = postOrder(root.Left, data, len)
	len = postOrder(root.Right, data, len)
	data[len] = root.Val
	len++
	return len
}

func midOrder(root *TreeNode, data []int, len int) int {
	if root == nil {
		return len
	}
	len = midOrder(root.Left, data, len)
	data[len] = root.Val
	len++
	len = midOrder(root.Right, data, len)
	return len
}

func preOrder(root *TreeNode, data []int, len int) int {
	if root == nil {
		return len
	}
	data[len] = root.Val
	len++
	len = preOrder(root.Left, data, len)
	len = preOrder(root.Right, data, len)
	return len
}