search
HomeDatabaseMysql Tutorial树形DP图画入门题解2 (HDU2196)

http://acm.hdu.edu.cn/showproblem.php?pid=2196 题意:一棵树N个节点,每条边有一个权w,求每个节点距离最远的路径长度。 2次深搜: 【第一次深搜】:求出在节点u的子树中,离u的最远,次远距离, 并标记 是从哪儿来的 。 int max_lenth[u] , max_id[u] ;

http://acm.hdu.edu.cn/showproblem.php?pid=2196

题意:一棵树N个节点,每条边有一个权值w,求每个节点距离最远的路径长度。


2次深搜:

 【第一次深搜】:求出在节点u的子树中,离u的最远,次远距离, 并标记是从哪儿来的

int max_lenth[u] , max_id[u] ;      最远距离, 转移儿子节点
int second_lenth[u] , second_id[u] ;  次远距离, 转移儿子节点

树形DP图画入门题解2 (HDU2196)


图1 :  第一次深搜, 当节点1的子树(绿色部分)遍历完回退的时候,最远次远距离只能是从(红色部分)2,6,9过来, 

          转移儿子节点就在2,6,9中选择。  也就是说max_id【1】 , second_id【1】 中存储的是2,6,9 中的某个。



树形DP图画入门题解2 (HDU2196)


图2 :  第一次深搜, 当节点2的子树(绿色部分)遍历完回退的时候,最远次远距离只能是从(红色部分)3,5过来, 

          转移儿子节点就在3,5中选择。  也就是说max_id【2】 , second_id【2】 中存储的是3,5 中的某个。


【第二次深搜】 : 求每个节点在整棵树上的最远、次远距离



树形DP图画入门题解2 (HDU2196)




图3 :  先看状态转移:

          对于节点2 , 最远距离、次远距离,来自2个地方(绿色部分)。

          绿色区域1、 节点2的子树部分,这个在第一次深搜已经保存好在绿色区域1离节点2的最远、次远距离。

          绿色区域2、 节点2的父亲节点1+父亲节点1的子树部分,这个在第一次深搜已经保存好在绿色区域2离节点1的最远、次远距离。

       那么只需要做个比较即可更新。

情况1 。  节点max_id[1] = 2,1的最远距离来自2 。 那么区域2中离节点2的最远距离second_lenth[1]。

             即  max_lenth[2] = max( max_lenth[2] , second_lenth[1] + w(1,2)) 。 

情况2 。  节点max_id[1] != 2,1的最远距离不是来自2 。 那么区域2中离节点2的最远距离max_lenth[1]。

             即  max_lenth[2] = max( max_lenth[2] , max_lenth[1]+w(1,2)) 。 

注意(树形DP最值得注意的地方): 

      dfs_1  , 先递归再DP

      dfs_2 ,   先DP再递归 

 


const int Max_N = 10008 ;

struct Edge{
       int v ;
       int w ;
       Edge(){}
       Edge(int i , int j):v(i) , w(j){}
};

vector<edge> List[Max_N] ;
int N ;
int max_lenth[Max_N] , max_id[Max_N] ;
int second_lenth[Max_N] , second_id[Max_N] ;

void dfs_1(int u , int father){
     int i , w , v ;
     for(i = 0 ; i <br>
<br>


</edge>
Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Explain the InnoDB Buffer Pool and its importance for performance.Explain the InnoDB Buffer Pool and its importance for performance.Apr 19, 2025 am 12:24 AM

InnoDBBufferPool reduces disk I/O by caching data and indexing pages, improving database performance. Its working principle includes: 1. Data reading: Read data from BufferPool; 2. Data writing: After modifying the data, write to BufferPool and refresh it to disk regularly; 3. Cache management: Use the LRU algorithm to manage cache pages; 4. Reading mechanism: Load adjacent data pages in advance. By sizing the BufferPool and using multiple instances, database performance can be optimized.

MySQL vs. Other Programming Languages: A ComparisonMySQL vs. Other Programming Languages: A ComparisonApr 19, 2025 am 12:22 AM

Compared with other programming languages, MySQL is mainly used to store and manage data, while other languages ​​such as Python, Java, and C are used for logical processing and application development. MySQL is known for its high performance, scalability and cross-platform support, suitable for data management needs, while other languages ​​have advantages in their respective fields such as data analytics, enterprise applications, and system programming.

Learning MySQL: A Step-by-Step Guide for New UsersLearning MySQL: A Step-by-Step Guide for New UsersApr 19, 2025 am 12:19 AM

MySQL is worth learning because it is a powerful open source database management system suitable for data storage, management and analysis. 1) MySQL is a relational database that uses SQL to operate data and is suitable for structured data management. 2) The SQL language is the key to interacting with MySQL and supports CRUD operations. 3) The working principle of MySQL includes client/server architecture, storage engine and query optimizer. 4) Basic usage includes creating databases and tables, and advanced usage involves joining tables using JOIN. 5) Common errors include syntax errors and permission issues, and debugging skills include checking syntax and using EXPLAIN commands. 6) Performance optimization involves the use of indexes, optimization of SQL statements and regular maintenance of databases.

MySQL: Essential Skills for Beginners to MasterMySQL: Essential Skills for Beginners to MasterApr 18, 2025 am 12:24 AM

MySQL is suitable for beginners to learn database skills. 1. Install MySQL server and client tools. 2. Understand basic SQL queries, such as SELECT. 3. Master data operations: create tables, insert, update, and delete data. 4. Learn advanced skills: subquery and window functions. 5. Debugging and optimization: Check syntax, use indexes, avoid SELECT*, and use LIMIT.

MySQL: Structured Data and Relational DatabasesMySQL: Structured Data and Relational DatabasesApr 18, 2025 am 12:22 AM

MySQL efficiently manages structured data through table structure and SQL query, and implements inter-table relationships through foreign keys. 1. Define the data format and type when creating a table. 2. Use foreign keys to establish relationships between tables. 3. Improve performance through indexing and query optimization. 4. Regularly backup and monitor databases to ensure data security and performance optimization.

MySQL: Key Features and Capabilities ExplainedMySQL: Key Features and Capabilities ExplainedApr 18, 2025 am 12:17 AM

MySQL is an open source relational database management system that is widely used in Web development. Its key features include: 1. Supports multiple storage engines, such as InnoDB and MyISAM, suitable for different scenarios; 2. Provides master-slave replication functions to facilitate load balancing and data backup; 3. Improve query efficiency through query optimization and index use.

The Purpose of SQL: Interacting with MySQL DatabasesThe Purpose of SQL: Interacting with MySQL DatabasesApr 18, 2025 am 12:12 AM

SQL is used to interact with MySQL database to realize data addition, deletion, modification, inspection and database design. 1) SQL performs data operations through SELECT, INSERT, UPDATE, DELETE statements; 2) Use CREATE, ALTER, DROP statements for database design and management; 3) Complex queries and data analysis are implemented through SQL to improve business decision-making efficiency.

MySQL for Beginners: Getting Started with Database ManagementMySQL for Beginners: Getting Started with Database ManagementApr 18, 2025 am 12:10 AM

The basic operations of MySQL include creating databases, tables, and using SQL to perform CRUD operations on data. 1. Create a database: CREATEDATABASEmy_first_db; 2. Create a table: CREATETABLEbooks(idINTAUTO_INCREMENTPRIMARYKEY, titleVARCHAR(100)NOTNULL, authorVARCHAR(100)NOTNULL, published_yearINT); 3. Insert data: INSERTINTObooks(title, author, published_year)VA

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

SublimeText3 English version

SublimeText3 English version

Recommended: Win version, supports code prompts!

mPDF

mPDF

mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

Atom editor mac version download

Atom editor mac version download

The most popular open source editor