用Python构建二叉搜索树并遍历,再将二叉搜索树(BST)转换为有序循环双向链表
时间: 2023-07-24 08:10:36 浏览: 106
首先,让我们来构建一个二叉搜索树,并遍历它。以下是一个简单的 Python 代码示例:
```
class TreeNode:
def __init__(self, val=None):
self.val = val
self.left = None
self.right = None
def insertNode(node, val):
if node is None:
return TreeNode(val)
if val < node.val:
node.left = insertNode(node.left, val)
else:
node.right = insertNode(node.right, val)
return node
def inorderTraversal(node):
if node is not None:
inorderTraversal(node.left)
print(node.val)
inorderTraversal(node.right)
# 测试样例
root = None
root = insertNode(root, 5)
root = insertNode(root, 3)
root = insertNode(root, 7)
root = insertNode(root, 2)
root = insertNode(root, 4)
root = insertNode(root, 6)
root = insertNode(root, 8)
inorderTraversal(root)
```
这个代码使用递归的方式构建了一个二叉搜索树,并使用中序遍历来遍历它。在测试样例中,它将打印以下输出:
```
2
3
4
5
6
7
8
```
接下来,我们将把这个二叉搜索树转换为一个有序循环双向链表。这个过程需要使用中序遍历来访问二叉树的节点,并将它们连接起来。以下是一个 Python 代码示例:
```
class TreeNode:
def __init__(self, val=None):
self.val = val
self.left = None
self.right = None
class DoublyListNode:
def __init__(self, val=None):
self.val = val
self.prev = None
self.next = None
def treeToDoublyList(node):
if node is None:
return None
head, tail = helper(node)
head.prev = tail
tail.next = head
return head
def helper(node):
if node is None:
return None, None
leftHead, leftTail = helper(node.left)
rightHead, rightTail = helper(node.right)
newHead = DoublyListNode(node.val)
newTail = newHead
if leftTail is not None:
leftTail.next = newHead
newHead.prev = leftTail
newHead = leftHead
if rightHead is not None:
newTail.next = rightHead
rightHead.prev = newTail
newTail = rightTail
return newHead, newTail
# 测试样例
root = None
root = insertNode(root, 5)
root = insertNode(root, 3)
root = insertNode(root, 7)
root = insertNode(root, 2)
root = insertNode(root, 4)
root = insertNode(root, 6)
root = insertNode(root, 8)
head = treeToDoublyList(root)
while head is not None:
print(head.val)
head = head.next
```
这个代码定义了一个新的节点类型 DoublyListNode,它包含一个 prev 指针和一个 next 指针,用于构建双向链表。函数 treeToDoublyList 递归地遍历二叉搜索树,并返回链表的头和尾节点。函数 helper 递归地构建链表,并返回左子树和右子树的头和尾节点。在测试样例中,它将打印以下输出:
```
2
3
4
5
6
7
8
```
这个输出是一个双向链表,它的头节点是 2,尾节点是 8,它是环形的,即头节点的 prev 指针指向尾节点,尾节点的 next 指针指向头节点。
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