一、589. N叉树的前序遍历

1.1、题目说明

1.2.1、递归

""" # Definition for a Node. class Node: def __init__(self, val, children): self.val = val self.children = children """ class Solution: def __init__(self) -> None: self.ret = [] def preorder(self, root: 'Node') -> List[int]: self.preorderTraversal(root) return self.ret def preorderTraversal(self, root: 'Node') -> List[int]: if root: self.ret.append(root.val) if root.children: for child in root.children: self.preorderTraversal(child)

1.2.2、迭代

class Solution: def __init__(self) -> None: self.ret = [] # 使用栈 迭代 def preorder(self, root: 'Node') -> List[int]: if not root: return [] que = [root] while que: queSize = len(que) for i in range(queSize): node = que.pop() self.ret.append(node.val) if node.children: for child in node.children[::-1]: print(child.val) que.append(child) return self.ret