python二叉树遍历代码if输出语句
时间: 2023-11-12 14:06:02 浏览: 42
以下是二叉树的前序遍历代码,其中包括了if输出语句:
```python
class TreeNode:
def __init__(self, val=0, left=None, right=None):
self.val = val
self.left = left
self.right = right
class Solution:
def preorderTraversal(self, root: TreeNode) -> List[int]:
if not root:
return []
res = []
stack = [root]
while stack:
node = stack.pop()
res.append(node.val)
if node.right:
stack.append(node.right)
if node.left:
stack.append(node.left)
return res
```
在这个代码中,if语句的作用是判断当前节点是否有左子节点或右子节点,如果有,则将左子节点或右子节点加入到栈中,以便后续遍历。
相关问题
python二叉树遍历代码if输出表示语句
以下是Python中二叉树的遍历代码,包括前序遍历、中序遍历和后序遍历,并附有if输出表示语句:
```python
# 定义二叉树节点类
class TreeNode:
def __init__(self, val=0, left=None, right=None):
self.val = val
self.left = left
self.right = right
# 前序遍历
def preorderTraversal(root: TreeNode) -> List[int]:
if not root:
return []
res = []
stack = [root]
while stack:
node = stack.pop()
res.append(node.val)
if node.right:
stack.append(node.right)
if node.left:
stack.append(node.left)
return res
# 中序遍历
def inorderTraversal(root: TreeNode) -> List[int]:
if not root:
return []
res = []
stack = []
cur = root
while cur or stack:
while cur:
stack.append(cur)
cur = cur.left
node = stack.pop()
res.append(node.val)
cur = node.right
return res
# 后序遍历
def postorderTraversal(root: TreeNode) -> List[int]:
if not root:
return []
res = []
stack = [root]
while stack:
node = stack.pop()
res.append(node.val)
if node.left:
stack.append(node.left)
if node.right:
stack.append(node.right)
return res[::-1]
```
其中,if输出表示语句可以在需要输出节点值的地方添加,例如:
```python
def inorderTraversal(root: TreeNode) -> List[int]:
if not root:
return []
res = []
stack = []
cur = root
while cur or stack:
while cur:
stack.append(cur)
cur = cur.left
node = stack.pop()
if node.val % 2 == 0: # 如果节点值为偶数,输出节点值
res.append(node.val)
cur = node.right
return res
```
python二叉树遍历代码
以下是Python实现二叉树遍历的代码示例:
定义二叉树节点类:
```python
class TreeNode:
def __init__(self, val=0, left=None, right=None):
self.val = val
self.left = left
self.right = right
```
先序遍历:
```python
def preorderTraversal(root):
if not root:
return []
res = []
stack = [root]
while stack:
node = stack.pop()
res.append(node.val)
if node.right:
stack.append(node.right)
if node.left:
stack.append(node.left)
return res
```
中序遍历:
```python
def inorderTraversal(root):
if not root:
return []
res = []
stack = []
while stack or root:
while root:
stack.append(root)
root = root.left
node = stack.pop()
res.append(node.val)
root = node.right
return res
```
后序遍历:
```python
def postorderTraversal(root):
if not root:
return []
res = []
stack = [root]
while stack:
node = stack.pop()
res.append(node.val)
if node.left:
stack.append(node.left)
if node.right:
stack.append(node.right)
return res[::-1]
```
其中,先序遍历和后序遍历使用了栈的思想,中序遍历使用了递归的方式。
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