题目链接 给n个数, 这n个数的值是从小到大的, 给出个n个数的出现次数. 然后用他们组成一个bst.访问每一个数的代价是这个点的深度*这个点访问的次数. 问你代价最小值是多少. 区间dp的时候, 如果l >= r, 那么返回0, l == r-1, 返回两个数中小的一个. 其他情况的话枚举分界点进行状态转移. #include <bits/stdc++.h> using namespace std; #define mem1(a) memset(a, -1, sizeof(a)) ;…

简单区间DP. #include<cstdio> #include<cstring> #include<cmath> #include<vector> #include<map> #include<queue> #include<stack> #include<algorithm> using namespace std; ; int n; int a[maxn], sum[maxn], dp[maxn][ma…

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…

p400 页最后一段 When j >= i , we need to select a root kr from among ki ... kj and then make an optimal binary search tree with keys ki ... kr-1 as its left subtree and an optimal binary search tree with keys kr+1 ... kj as its right subtree.What happens…

问题 该问题的实际应用 Suppose that we are designing a program to translate text from English to French. For each occurrence of each English word in the text, we need to look up its French equivalent. We could perform these lookup operations by building a binar…

UVA 1264 - Binary Search Tree 题目链接 题意:给定一个序列,插入二叉排序树,问有多少中序列插入后和这个树是同样的(包含原序列) 思路:先建树,然后dfs一遍,对于一个子树而言,仅仅要保证左边和右边顺序对就能够了,所以种数为C(左右结点总数,左结点),然后依据乘法原理乘上左右子树的情况就可以 代码: #include <cstdio> #include <cstring> typedef long long ll; const int MAXNODE =…

二叉树(Binary Tree)是最简单的树形数据结构,然而却十分精妙.其衍生出各种算法,以致于占据了数据结构的半壁江山.STL中大名顶顶的关联容器--集合(set).映射(map)便是使用二叉树实现.由于篇幅有限,此处仅作一般介绍(如果想要完全了解二叉树以及其衍生出的各种算法,恐怕要写8~10篇). 1)二叉树(Binary Tree) 顾名思义,就是一个节点分出两个节点,称其为左右子节点:每个子节点又可以分出两个子节点,这样递归分叉,其形状很像一颗倒着的树.二叉树限制了每个节点最多有两个子节…

Given an array of numbers, verify whether it is the correct preorder traversal sequence of a binary search tree. You may assume each number in the sequence is unique. Follow up: Could you do it using only constant space complexity? 这道题让给了我们一个一维数组,让我们…

题目要求 Given a binary search tree and the lowest and highest boundaries as L and R, trim the tree so that all its elements lies in [L, R] (R >= L). You might need to change the root of the tree, so the result should return the new root of the trimmed b…

[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…