solution.go

package leetcode

/*
 * @lc app=leetcode.cn id=103 lang=golang
 *
 * [103] 二叉树的锯齿形层次遍历
 */

// @lc code=start
/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */

type TreeNode struct {
	Val   int
	Left  *TreeNode
	Right *TreeNode
}

func zigzagLevelOrder(root *TreeNode) [][]int {
	res := [][]int{}
	if root == nil {
		return res
	}
	queue := []*TreeNode{root}
	for level := 0; len(queue) > 0; level++ {
		l := len(queue)
		list := []int{}
		for i := 0; i < l; i++ {
			node := queue[i]
			if level%2 == 0 {
				list = append(list, node.Val)
			} else {
				list = append([]int{node.Val}, list...)
			}
			if node.Left != nil {
				queue = append(queue, node.Left)
			}
			if node.Right != nil {
				queue = append(queue, node.Right)
			}
		}
		queue = queue[l:]
		res = append(res, list)
	}
	return res
}

// @lc code=end