[LeetCode]Binary Search Tree Iterator
来源:互联网 发布:手机改图软件 编辑:程序博客网 时间:2024/06/05 09:13
Question
Implement an iterator over a binary search tree (BST). Your iterator will be initialized with the root node of a BST.
Calling next()
will return the next smallest number in the BST.
Note: next()
and hasNext()
should run in average O(1) time and uses O(h) memory, where h is the height of the tree.
本题难度Medium。
题意
设计一个迭代器类,该类可以以Avg O(1)的时间枚举二叉查找树的最小值,且仅使用
O(h)空间(难点在此)
栈
复杂度
时间 O(1) 空间 O(h)
Example
10 / \1 11 \ \ 6 12
思路
建立一个堆栈,先将最左边的结点从大到小压入栈,这样的话,为了实现迭代即返回下一个node的next()函数就要考虑右边的结点。比如Example中的BST,stack第一次pop出来的结点是1,然后就应该把它的右子树结点6压入stack;又如pop出了root结点10以后,就要把11压入堆栈,这样,在pop出11之后,再将12压入堆栈。如此,实现next()函数。
代码
public class BSTIterator { private Stack<TreeNode> stk=new Stack<>(); public BSTIterator(TreeNode root) { leftTraversal(root); } private void leftTraversal(TreeNode root){ while(root!=null){ stk.push(root); root=root.left; } } /** @return whether we have a next smallest number */ public boolean hasNext() { return !stk.isEmpty(); } /** @return the next smallest number */ public int next() { TreeNode n=stk.pop(); leftTraversal(n.right); return n.val; }}
参考
[LintCode] Binary Search Tree Iterator
0 0
- [LeetCode] Binary Search Tree Iterator
- LeetCode Binary Search Tree Iterator
- Leetcode Binary Search Tree Iterator
- [LeetCode] Binary Search Tree Iterator
- Leetcode: Binary Search Tree Iterator
- leetcode:Binary Search Tree Iterator
- Binary Search Tree Iterator --- LeetCode
- LeetCode--Binary Search Tree Iterator
- Leetcode:Binary Search Tree Iterator
- [LeetCode]Binary Search Tree Iterator
- LeetCode: Binary Search Tree Iterator
- *LeetCode-Binary Search Tree Iterator
- [Leetcode]Binary Search Tree Iterator
- LeetCode::Binary Search Tree Iterator
- [Leetcode]Binary Search Tree Iterator
- leetcode: Binary Search Tree Iterator
- Leetcode: Binary Search Tree Iterator
- LeetCode | Binary Search Tree Iterator
- 如何在Linux服务器上设置rsync驻留服务
- asp.net mvc使用邮箱找回密码功能的详细步骤
- Android网络状态之ConnectivityManager
- 关于hosts
- CSS学习笔记1
- [LeetCode]Binary Search Tree Iterator
- 如何在linux环境下使用r语言
- win+caffe mnist实例运行(禁止转载)
- lintcode_100题
- code formatter
- python zio库的ctf常用函数
- 打印图形
- Maven管理项目时 使用package命令报错:There are test failures
- Angular项目构建指南 - 不再为angular构建而犹豫不决