层序遍历

/*** Definition for a binary tree node.* type TreeNode struct {*     Val int*     Left *TreeNode*     Right *TreeNode* }*/import ("container/list"
)func levelOrder(root *TreeNode) [][]int {// 思路1：此处肯定要使用队列result := [][]int{}if root == nil {return result}stack := list.New()stack.PushBack(root)for stack.Len() > 0 {stackLength := stack.Len()// 遍历每一层的所有节点newLis := []int{}for i := 0; i < stackLength; i++ {top := stack.Remove(stack.Front())node := top.(*TreeNode)newLis = append(newLis, node.Val)if node.Left != nil {stack.PushBack(node.Left)}if node.Right != nil {stack.PushBack(node.Right)}}result = append(result, newLis)}return result
}