二叉树的遍历完整代码

以下是二叉树的三种遍历方式的完整代码：

. 前序遍历：

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = rightdef preOrder(root):
    if root is None:
        return
    print(root.val, end=" ")
    preOrder(root.left)
    preOrder(root.right)

# 创建二叉树
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
root.left.left = TreeNode(4)
root.left.right = TreeNode(5)

# 前序遍历二叉树
preOrder(root)

2. 中序遍历：

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def inOrder(root):
    if root is None:
        return
    inOrder(root.left)
    print(root.val, end=" ")
    inOrder(root.right)

# 创建二叉树
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
root.left.left = TreeNode(4)
root.left.right = TreeNode(5)

# 中序遍历二叉树
inOrder(root)

3. 后序遍历：

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def postOrder(root):
    if root is None:
        return
    postOrder(root.left)
    postOrder(root.right)
    print(root.val, end=" ")

# 创建二叉树
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
root.left.left = TreeNode(4)
root.left.right = TreeNode(5)

# 后序遍历二叉树
postOrder(root)