python-leetcode面试题解之第144题二叉树的前序遍历-题解.zip

# Definition for a binary tree node. # class TreeNode(object): # def __init__(self, x): # self.val = x # self.left = None # self.right = None class Solution(object): # def __init__(self): # self.result = [] # # def preorderTraversal(self, root): # """ # :type root: TreeNode # :rtype: List[int] # """ # if root is None: # return [] # self.preorderTraversalHelper(root) # return self.result # # def preorderTraversalHelper(self, node): # if node is None: # return # self.result.append(node.val) # self.preorderTraversalHelper(node.left) # self.preorderTraversalHelper(node.right) def preorderTraversal(self, root): # stack if root is None: return [] res = [] stack = [root] while len(stack) > 0: curr = stack.pop() res.append(curr.val) if curr.right is not None: stack.append(curr.right) if curr.left is not None: stack.append(curr.left) return res