LeetCode 102. 二叉树的层序遍历BFS

/*** Definition for a binary tree node.* type TreeNode struct {*     Val int*     Left *TreeNode*     Right *TreeNode* }*/funclevelOrder(root*TreeNode) [][]int {
res :=make([][]int, 0)
queue :=make([]*TreeNode, 0)
ifroot!=nil {
queue=append(queue, root) // 首先，根节点入队    }
forlen(queue) >0 {
subRes :=make([]int, 0)
length :=len(queue)    // 提前缓存上一轮queue大小，避免在内循环中append导致queue长度变化fori :=0; i<length; i++ {
root :=queue[0]
subRes=append(subRes, root.Val)
queue=queue[1:]   // popifroot.Left!=nil {
queue=append(queue, root.Left)
            }
ifroot.Right!=nil {
queue=append(queue, root.Right)
            }
        }
res=append(res, subRes)
    }
returnres}