8.13笔记

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本文深入解析了二叉搜索树中第K小元素查找算法，以及链表中重复元素删除与区间反转的高效实现。通过具体实例，详细讲解了算法的设计思路与代码实现，为读者提供了一个理解链表和二叉树操作的良好途径。

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230. 二叉搜索树中第K小的元素

class Solution(object):
    def kthSmallest(self, root, k):
        """
        :type root: TreeNode
        :type k: int
        :rtype: int
        """
        stack = []
        while stack or root:
            while root:
                stack.append(root)
                root = root.left
            root = stack.pop()
            k -= 1
            if k == 0:
                return root.val
            root = root.right

82. 删除排序链表中的重复元素 II

class Solution(object):
    def deleteDuplicates(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        pre = res = ListNode(0)
        pre.next = head
        while head and head.next:
            if head.val == head.next.val:
                while head.next and head.val == head.next.val:
                    head = head.next
                head = head.next
                pre.next = head
            else:
                pre = pre.next
                head = head.next
        return res.next

92. 反转链表 II

    def reverseBetween(self, head, m, n):
        """
        :type head: ListNode
        :type m: int
        :type n: int
        :rtype: ListNode
        """
        if n == m:
            return head
        count = 1
        res = ListNode(None)
        res.next = head
        pre = res
        while count < m:
            pre = pre.next
            count += 1
        newhead,head,tail = None,pre.next,pre.next
        for i in range(n-m+1):
            head.next,newhead,head=newhead,head,head.next
        pre.next,tail.next = newhead,head
        return res.next