590. N叉树的后序遍历

590. N叉树的后序遍历

返回其后序遍历: [5,6,3,2,4,1].

type Node struct {
    Val      int
    Children []*Node
}
func postorder(root *Node) []int {
    if root==nil{
        return nil
    }
    res :=make([]int,0)
    helper(root,&res)
    return res
}
func helper(root *Node,res *[]int){
    if root==nil{
        return
    }
    for _,v:=range root.Children{
        helper(v,res)
    }
    *res = append(*res,root.Val)
}

迭代实现

func postorder(root *Node) []int {
    if root==nil{
        return nil
    }
    stack := make([]*Node,0)
    stack = append(stack,root)
    res := make([]int,0)
    for len(stack)>0{
        node := stack[len(stack)-1]
        stack = stack[:len(stack)-1]
        res = append([]int{node.Val},res...)
        for i:=0;i<len(node.Children);i++{
            stack = append(stack,node.Children[i])
        }
    }
    return res
}