package top100liked

// https://leetcode.cn/problems/binary-tree-level-order-traversal/?envType=study-plan-v2&envId=top-100-liked

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

func levelOrder(root *TreeNode) [][]int {
	if root == nil {
		return [][]int{}
	}

	queue := []*TreeNode{root}
	res := [][]int{}
	for len(queue) > 0 {
		currentLayerRes := []int{}
		tmpQueue := []*TreeNode{}
		for i := range queue {
			currentNode := queue[i]
			currentLayerRes = append(currentLayerRes, currentNode.Val)
			if currentNode.Left != nil {
				tmpQueue = append(tmpQueue, currentNode.Left)
			}
			if currentNode.Right != nil {
				tmpQueue = append(tmpQueue, currentNode.Right)
			}
		}
		queue = tmpQueue
		res = append(res, currentLayerRes)
	}
	return res
}