107.二叉树的层序遍历-ii.go

/*
 * @lc app=leetcode.cn id=107 lang=golang
 *
 * [107] 二叉树的层序遍历 II
 */

// @lc code=start
/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func levelOrderBottom(root *TreeNode) [][]int {
	res := [][]int{}
	if root == nil {
		return res
	}

	queue := list.New()
	queue.PushBack(root)

	for queue.Len() > 0 {
		length := queue.Len()
		tmpArr := []int{}
		for i := 0; i < length; i++ {
			node := queue.Remove(queue.Front()).(*TreeNode)
			if node.Left != nil {
				queue.PushBack(node.Left)
			}
			if node.Right != nil {
				queue.PushBack(node.Right)
			}
			tmpArr = append(tmpArr, node.Val)
		}
		res = append(res, tmpArr)
	}

	for i := 0; i < len(res)/2; i++ {
		res[i], res[len(res)-1-i] = res[len(res)-1-i], res[i]
	}

	return res

}

// @lc code=end