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. 1 3 3 2 1 \ / / / \ \ 3 2 1 1 3 2 / / \ \ 2 1 2 3 代码: class Solution { public: int numTrees(i…

当数组为1,2,3,4,...,n时,基于以下原则构建的BST树具有唯一性: 以i为根节点的树,其左子树由[1,i-1]构成,其右子树由[i+1, n]构成. 我们假定f(i)为以[1,i]能产生的Unique Binary Search Tree的数目,则 如果数组为空,毫无疑问,只有一种BST,即空树,f(0)=1. 如果数组仅有一个元素1,只有一种BST,单个节点,f(1)=1. 如果数组有两个元素1,2,那么有如下两种可能: 1             2    \         /…

题目: Given n, generate all structurally unique BST's (binary search trees) that store values 1...n. For example,Given n = 3, your program should return all 5 unique BST's shown below. 1 3 3 2 1 \ / / / \ \ 3 2 1 1 3 2 / / \ \ 2 1 2 3 代码: /** * Definit…

提到二叉查找树,就得想到二叉查找树的递归定义, 左子树的节点值都小于根节点,右子树的节点值都大于根节点. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 给定一个n,问有多少个不同的二叉查找树,使得每个节点的值为 1...n? 例如, 给定n=3,你的程序应该返回所有的这5个不同的二叉排序树的个数. 1 3 3 2 1 \ / / / \ \ 3 2 1 1 3 2 / / \…

题目: 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. The right subtree of a node contains only nodes with…

题目: 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 devise a constant space solution? confused what "{1,#,2,3}&…

首先我们要注意到一个性质:由于根与右子树的根奇偶性相同,那么根的奇偶性与\(N\)相同 然后我们发现对于一个完美树,他的左右两个儿子都是完美树 也就是说,一颗完美树是由两棵完美树拼成的 注意到另一个性质:由于权值是一个排列,假设根节点为\(x\),那么左子树的范围是\([1, x - 1]\),右子树为\([x + 1, n]\) 由于根节点和\(N\)奇偶性相同,那么左子树的大小与\(N\)的奇偶性相反,所以右子树大小为偶数 如果子树区间为\([l, r]\),那么其实可以把它看成\([1,…

一天一道LeetCode 本系列文章已全部上传至我的github,地址:ZeeCoder's Github 欢迎大家关注我的新浪微博,我的新浪微博 欢迎转载,转载请注明出处 (一)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. (二)解题…

[LeetCode]95. Unique Binary Search Trees II 解题报告(Python) 标签(空格分隔): LeetCode 作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.me/ 题目地址:https://leetcode.com/problems/unique-binary-search-trees-ii/description/ 题目描述: Given an integer n, generate all s…

Unique Binary Search Trees II Given n, generate all structurally unique BST's (binary search trees) that store values 1...n. For example,Given n = 3, your program should return all 5 unique BST's shown below. 1 3 3 2 1 \ / / / \ \ 3 2 1 1 3 2 / / \ \…