iteye_17352的博客

Given an array of integers, find out whether there are two distinct indices i and j in the array such that the difference between nums[i] and nums[j] is at most t and the difference between i and j i...

[分析] 参考[url]https://leetcode.com/discuss/59728/10-and-4-lines-o-h-java-c[/url] & [url]https://leetcode.com/discuss/59787/share-my-java-recursive-solution[/url] 不理解参考代码中为什么最后需要额外判断left.val > p.val ...

[分析] 最近公共祖先(LCA)是一个经典问题，以前没有好好研究过这个问题，不知道还有个Tarjan算法，今天开了眼界。一般有两种方法分别适用不同场景： 1）递归算法，适合在线单次查询，如本题； 2）Tarjan算法，适合批量查询，输入是一颗树和N对定点，为每个顶点（u,v）确定LCA。 有兴趣的同学看参考[url]https://github.com/julycoding/The-Ar...

[分析] 思路1：遍历所有节点找到和 target最接近的 k 个元素，能否有个数据结构在遍历过程中维护已遍历元素离target最近的呢？PriorityQueue具备这种能力。我们需要个最小堆，堆元素需要保存两个信息，一个是树节点元素值，一个是这个元素和target的差的绝对值。但PriorityQueue是没有“堆底”概念的，当堆的size 增长到 k 后，如何删除堆中最大元素呢？ 为实现删...

Given n nodes labeled from 0 to n - 1 and a list of undirected edges (each edge is a pair of nodes), write a function to check whether these edges make up a valid tree. For example: Given n = 5 ...

Given a non-empty binary search tree and a target value, find k values in the BST that are closest to the target. Note: Given target value is a floating point. You may assume k is always valid, t...

Given a binary tree where all the right nodes are either leaf nodes with a sibling (a left node that shares the same parent node) or empty, flip it upside down and turn it into a tree where the origin...

[分析] 思路1：暴力法，遍历当前待检查数组，找到第一个大于数组起始位置的位置i，则 i 为右子树根节点，然后递归判断左右子树。对于根节点，最坏情况下要遍历整个数组，时间为O（N），因为要递归检查每个节点，因此总的时间复杂度是O（N^2）。 思路2：参考StefanPochmann大神的作品[url]https://leetcode.com/discuss/51543/java-o-n-and...

Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST. [分析] 思路1复杂度是O（nlogn），实现过程中发现自己二指针法一开始是写错的，错误的结果是二分后左边会比右边多两个元素，在Reorder List中这种写法之所以也能...

[分析] 思路1： 递归中序遍历，返回中序遍历中的第k个数。 思路2： 迭代方式实现的中序遍历，遍历到第k个数即返回。 思路3： 如果可以修改数结构，增加一个leftCount属性，记录当前节点左子树节点个数。 [ref] [url]http://bookshadow.com/weblog/2015/07/02/leetcode-kth-smallest-element-bst/[/...

Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. Note: A solution using O(n) space is pretty straight forward. Could you devis...

Given a binary tree, determine if it is a valid binary search tree (BST). Assume a BST is defined as follows: The left subtree of a node contains only nodes with keys less than the node's key. ...

Definition of a complete binary tree from Wikipedia: In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible...

[题目] Given n, how many structurally unique BST's (binary search trees) that store values 1...n? For example,Given n = 3, there are a total of 5 unique BST's.   [分析] n个节点的BST的结构数等于从1到n依次为root节点对应...