题解 | #从上往下打印二叉树#

package main

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

func PrintFromTopToBottom( root *TreeNode ) []int {
    var ans []int
    if root == nil { //空树
        return ans
    }
    queue := []*TreeNode{root} 
    for len(queue) > 0 {
        node := queue[0] 
        queue = queue[1:] 
        ans = append(ans, node.Val) 
        if node.Left != nil {
            queue = append(queue, node.Left) 
        }
        if node.Right != nil {
            queue = append(queue, node.Right) 
        }
    }
    return ans
}