package q103

import "slices"

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

func zigzagLevelOrder(root *TreeNode) [][]int {
	ret := [][]int{}
	if root == nil {
		return ret
	}

	dpth := 1
	buf := make([]int, 512)
	row := buf[:0]

	type qElem struct {
		depth int
		node  *TreeNode
	}
	queue := make([]qElem, 0, 256)
	queue = append(queue, qElem{depth: 1, node: root})
	for ; len(queue) > 0; queue = queue[1:] {
		c := queue[0]
		if c.depth > dpth {
			if dpth%2 == 0 {
				slices.Reverse(row)
			}
			ret = append(ret, make([]int, len(row)))
			copy(ret[len(ret)-1], row)

			dpth = c.depth
			row = buf[:0]
		}

		row = append(row, c.node.Val)
		if c.node.Left != nil {
			queue = append(queue, qElem{depth: c.depth + 1, node: c.node.Left})
		}
		if c.node.Right != nil {
			queue = append(queue, qElem{depth: c.depth + 1, node: c.node.Right})
		}
	}
	if dpth%2 == 0 {
		slices.Reverse(row)
	}
	ret = append(ret, row)
	return ret
}

var _ = zigzagLevelOrder