题目大意:给你一个$[0,1]$之间等概率随机序列,你需要把这个序列插入到一棵$treap$中,问这棵$treap$的期望深度,请对于$[1,n]$中的每个深度分别输出它的概率(实数,保留五位小数). $treap$的优先级之也是在$[0,1]$中等概率随机出来的. ps:这个$[0,1]$的随机非常$niubi$,任意一个$[0,1]$间的实数被选中的概率是$0$ 这一题有一个很特殊的性质:两个序列都是等概率随机出来的. 在没有相同数的情况下,我们发现$treap$最终的形态跟数值插入的顺序是…

题目描述 \(\forall 0\leq i<n\),求有多少棵\(n\)个点,权值和优先级完全随机的treap的树高为\(i\). \(n\leq 30000\) 题解 设\(f_{i,j}\)为\(j\)个点的树,树高不超过为\(i\)的概率 \[ f_{i,j}=\frac{1}{j}\sum_{k=1}^{j}f_{i-1,j-1}\times f_{i-1,j-k} \] 枚举一个点左子树大小\(k-1\),那么右子树大小为\(j-k\).且这个点的优先级为这\(j\)个点最小的概率是…

[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…

链接:https://leetcode.com/tag/binary-search-tree/ [220]Contains Duplicate III (2019年4月20日) (好题) Given an array of integers, find out whether there are two distinct indices i and j in the array such that the absolute difference between nums[i] and nums[…

Validate Binary Search Tree 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 c…

Recover Binary Search Tree 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? 中序…

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 keys…

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 keys…

时间挤挤总是有的 太久不做题,脑子都生锈了.来道水题练练手 题目地址: https://leetcode.com/problems/binary-search-tree-iterator/ 题目内容: 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…

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 keys…

Binary Search Tree Iterator 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…

题目: Given a binary tree, determine if it is a valid binary search tree (BST). 知识点:BST的特点: 1.一个节点的左子树的全部点都小于或等于这个点的值.右子树的全部节点的值大于该节点的值: 2.最左节点值最小,最右节点值最大. 3.中序遍历结果值是一个非降的数列 问题:假设用Integer.MAX_VALUE会过不了測试用例,但是依照TreeNode中的定义.val值也是int呀.没办法用了Long.假设谁知道,麻烦…

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 keys…

题目如下: Given the root of a binary search tree with distinct values, modify it so that every node has a new value equal to the sum of the values of the original tree that are greater than or equal to node.val. As a reminder, a binary search tree is a t…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 保存全部节点 只保留左节点 日期 题目地址:https://leetcode.com/problems/binary-search-tree-iterator/description/ 题目描述 Implement an iterator over a binary search tree (BST). Your iterator will be i…

题意 求 \(n\) 个点的 Treap 深度为 \(h=0,1,2,\cdots,n\) 的概率. Treap 是一个随机二叉树,每个节点有权值和优先级,权值和优先级都是 \([0,1]\) 中的随机实数.niubi 的是,由于随机的实数精度足够高,你可以近似认为任意两个权值.任意两个优先级相同的概率是 \(0\). \(n\le 30000\) 题解 又是神题,我他吗都做不来 官方题解大概是这样,但本蒟蒻完全没看懂,于是只好向 scb 大佬请教了另一种思考方法(得到的 dp 式子一样). 考…

需要注意的是,左子树的所有节点都要比根节点小,而非只是其左孩子比其小,右子树同样.这是很容易出错的一点是,很多人往往只考虑了每个根节点比其左孩子大比其右孩子小.如下面非二分查找树,如果只比较节点和其左右孩子的关系大小,它是满足的. 5  /     \4      10      /      \    3        11 错误代码: /** * Definition for a binary tree node. * function TreeNode(val) { * this.val…

Problem Link: https://oj.leetcode.com/problems/recover-binary-search-tree/ We know that the inorder traversal of a binary search tree should be a sorted array. Therefore, we can compare each node with its previous node in the inorder to find the two…

Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. 题意: 一颗二叉搜索树中有2个结点的元素被误换了,要求恢复二叉搜索树的原状. 思路: 中序遍历BST,若发现一次逆序,说明是两个相连结点的误换,直接交换结点的值:若发现两次逆序,则为不相连的两个结点误换,交换错误的结点即可.用一个变量保存先前结点的状态,若发生逆序则记…

Recover Binary Search Tree Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. 互换二叉搜索树中两个位置错误的节点. 思路: 预设三个指针pre,p1,p2.p1用来指向第一个出错的节点,p2用来指向第二个出错的节点. 出错情况有两种,即p1和p2相邻,p1和p2不相邻. 中序遍历此二叉树,用…

Validate Binary Search Tree 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 c…

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 keys…

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? 题解:需要找到二叉搜索树中乱序的两个节点,并把它们交换回来…

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 / / \ \…

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 这次的题目要求是得到所有的树. 我的思路:…

给定结点数n,结点值为1,2,...,n,求由这些结点可以构成的所有二叉查找树. 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…

本文为大便一箩筐的原创内容,转载请注明出处,谢谢:http://www.cnblogs.com/dbylk/p/4048209.html 原题: 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…

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 思路: 找到一个数作为根结点,剩余…

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 解题: 按照动态规划的思路,求1~n的全部…

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  …