[LeetCode Python3] 144. Binary Tree Preorder Traversal +递归+迭代

SincX

于 2020-12-27 15:57:18 发布

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144. Binary Tree Preorder Traversal

递归

class Solution:
    def preorderTraversal(self, root: TreeNode) -> List[int]:
        if not root:
            return []
        res = [root.val]
        if root.left:
            res += self.preorderTraversal(root.left)
        if root.right:
            res += self.preorderTraversal(root.right)
        return res

迭代

class Solution:
    def preorderTraversal(self, root: TreeNode) -> List[int]:
        if not root:
            return []
        que = [root]
        res = []
        while que:
            tmp = que.pop()
            res.append(tmp.val)
            if tmp.right:
                que.append(tmp.right)
            if tmp.left:
                que.append(tmp.left)
        return res