题解 | #按之字形顺序打印二叉树#

package main
import . "nc_tools"

func Print( pRoot *TreeNode ) [][]int {
    // write code here
    if pRoot == nil {
        return [][]int{}
    }

    queue := []*TreeNode{pRoot}
    levels := [][]int{}

    for len(queue) > 0 {
        n := len(queue)
        level := []int{}

        for i := 0; i < n; i++ {
            pRoot = queue[0]
            queue = queue[1:]

            level = append(level, pRoot.Val)
            if pRoot.Left != nil {
                queue = append(queue, pRoot.Left)
            }
            if pRoot.Right != nil {
                queue = append(queue, pRoot.Right)
            }
        }

        k1 := len(level)                    //这里注意，内层【】，翻转的都是这里面的
        k2 := len(levels)                   //这里也要注意，外层【】，只有判断奇偶的时候用
        if k2 % 2 == 1 {
            for i := 0; i < k1/2; i++ {
                level[i], level[k1-1-i] = level[k1-1-i], level[i]
            }
        }
        levels = append(levels, level)
    }
    return levels
}