面试题32 - II. 从上到下打印二叉树 II

面试题32 - II. 从上到下打印二叉树 II

1每次把所以的数组节点都出栈
2然后把所以的子节点元素都入栈
3直到所有栈为空

package main
import "fmt"
type TreeNode struct {
    Val   int
    Left  *TreeNode
    Right *TreeNode
}
func levelOrder(root *TreeNode) [][]int {
    if root == nil {
        return nil
    }
    nodes := make([]*TreeNode, 0)
    nodes = append(nodes, root)
    var res [][]int
    for len(nodes) > 0 {
        var nodeList []*TreeNode
        var values []int
        for i := 0; i < len(nodes); i++ {
            node := nodes[i]
            if node.Left != nil {
                nodeList = append(nodeList, node.Left)
            }
            if node.Right != nil {
                nodeList = append(nodeList, node.Right)
            }
            values = append(values, node.Val)
        }
        if len(values) > 0 {
            res = append(res, values, )
        }
        nodes = append(nodes[len(nodes):], nodeList...)
    }
    return res
}
func main() {
    three := &TreeNode{Val: 3}
    nine := &TreeNode{Val: 9}
    three.Left = nine
    twenty := &TreeNode{Val: 20}
    three.Right = twenty
    fifteen := &TreeNode{Val: 15}
    twenty.Left = fifteen
    severn := &TreeNode{Val: 7}
    twenty.Right = severn
    fmt.Println(levelOrder(three))
}