题解 | #实现二叉树先序，中序和后序遍历#

package main
import . "nc_tools"
/*
 * type TreeNode struct {
 *   Val int
 *   Left *TreeNode
 *   Right *TreeNode
 * }
 */

/**
 * 
 * @param root TreeNode类 the root of binary tree
 * @return int整型二维数组
*/
var pre = make([]int, 0)
var mid = make([]int, 0)
var nex = make([]int, 0)
func threeOrders( root *TreeNode ) [][]int {
    preTrave(root)
    midTrave(root)
    nexTrave(root)
    
    res := make([][]int, 3)
    res[0] = pre
    res[1] = mid
    res[2] = nex    
    return res
}

func preTrave(root *TreeNode ) {
    if root == nil {
        return 
    }
    pre = append(pre, root.Val)
    preTrave(root.Left)
    preTrave(root.Right)
    
}

func midTrave(root *TreeNode ) {
    if root == nil {
        return 
    }
    midTrave(root.Left)
    mid = append(mid, root.Val)
    midTrave(root.Right)
    
}


func nexTrave(root *TreeNode ) {
    if root == nil {
        return 
    }
    nexTrave(root.Left)
    nexTrave(root.Right)
    nex = append(nex, root.Val)
    
}