```
/**
* @description: 107. Binary Tree Level Order Traversal II
Given the root of a binary tree, return the bottom-up level order traversal of its nodes' values. (i.e., from left to right, level by level from leaf to root).
* @return: 自底向上，从左到右的顺序输出节点* @author: kami
* @关键词：层序遍历,队列，追加在结果的头部* @date: 2021/7/4 9:50
*/
func levelOrderBottom(root *TreeNode) [][]int {
if root ==nil {
return [][]int{}
}
var res =make([][]int, 1)
var queue =make([]*TreeNode, 1)
queue[0] = root
var first = []int{root.Val}
res[0] = first
for {
var size =len(queue)
var curNum []int
for i :=0; i < size; i++ {
if queue[i].Left !=nil {
queue =append(queue, queue[i].Left)
curNum =append(curNum, queue[i].Left.Val)
}
if queue[i].Right !=nil {
queue =append(queue, queue[i].Right)
curNum =append(curNum, queue[i].Right.Val)
}
}
if len(curNum) <1 {
return res
}
queue =append(queue[:0], queue[size:]...)
var temp = [][]int{
curNum,
}
res =append(temp, res...)
}
}
```
