"""
Definition of TreeNode:
class TreeNode:
def __init__(self, val):
self.val = val
self.left, self.right = None, None
"""
class Solution:
"""
@param root: A Tree
@return: Preorder in ArrayList which contains node values.
"""
def preorderTraversal(self, root):
# write your code here
if not root: return []
results = []
left = self.preorderTraversal(root.left)
right = self.preorderTraversal(root.right)
results.append(root.val)
results.extend(left)
results.extend(right)
return results
"""
Definition of TreeNode:
class TreeNode:
def __init__(self, val):
self.val = val
self.left, self.right = None, None
"""
class Solution:
"""
@param root: A Tree
@return: Preorder in ArrayList which contains node values.
"""
def preorderTraversal(self, root):
# write your code here
return [root.val] + self.preorderTraversal(root.left) + self.preorderTraversal(root.right) if root else []
非递归版本:
"""
Definition of TreeNode:
class TreeNode:
def __init__(self, val):
self.val = val
self.left, self.right = None, None
"""
class Solution:
"""
@param root: A Tree
@return: Preorder in ArrayList which contains node values.
"""
def preorderTraversal(self, root):
# write your code here
#非递归
results = []
stack = [root]
while stack:
pop_node = stack.pop(0)
results.append(pop_node.val)
if pop_node.left:
stack.append(pop_node.left)
if pop_node.right:
stack.append(pop_node.right)
return results
