二叉树的前序、中序、后序遍历（python）

前序：

class Solution:
    def preorderTraversal(self, root: TreeNode) -> List[int]:
        res=[]
        stack=[]
        while root or stack:
            if root:
                stack.append(root)
                res.append(root.val)
                root=root.left
            else:
                root=stack.pop()
                root=root.right
        return res

后序:

class Solution:
    def postorderTraversal(self, root: TreeNode) -> List[int]:
        stack=[]
        res=[]
        while root or stack:
            if root:
                stack.append(root)
                res.append(root.val)
                root=root.right
            else:
                root=stack.pop()
                root=root.left
        return res[::-1]

中序：

class Solution:
    def inorderTraversal(self, root: TreeNode) -> List[int]:
        stack=[]
        res=[]
        while stack or root:
            if root:
                stack.append(root)
                root=root.left
            else:
                root = stack.pop()
                res.append(root.val)
                root=root.right
        return res

2019-12-27 21:56:55