


Codeforces Round #277 (Div. 2)D (tree DP counting class)_html/css_WEB-ITnose
Jun 24, 2016 am 11:54 AM
D. Valid Sets
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
As you know, an undirected connected graph with?n?nodes and?n?-?1?edges is called a?tree. You are given an integer?d?and a tree consisting of?n?nodes. Each node?i?has a value?ai?associated with it.
We call a set?S?of tree nodes?valid?if following conditions are satisfied:
- S?is non-empty.
- S?is connected. In other words, if nodes?u?and?v?are in?S, then all nodes lying on the simple path between?u?and?v?should also be presented in?S.
- .
Your task is to count the number of valid sets. Since the result can be very large, you must print its remainder modulo?1000000007(109? ?7).
Input
The first line contains two space-separated integers?d?(0?≤?d?≤?2000) and?n?(1?≤?n?≤?2000).
The second line contains?n?space-separated positive integers?a1,?a2,?...,?an(1?≤?ai?≤?2000).
Then the next?n?-?1?line each contain pair of integers?u?and?v?(1?≤?u,?v?≤?n) denoting that there is an edge between?u?and?v. It is guaranteed that these edges form a tree.
Output
Print the number of valid sets modulo?1000000007.
Sample test(s)
input
1 42 1 3 21 21 33 4
output
input
0 31 2 31 22 3
output
input
4 87 8 7 5 4 6 4 101 61 25 81 33 56 73 4
output
41
Note
In the first sample, there are exactly 8 valid sets:?{1},?{2},?{3},?{4},?{1,?2},?{1,?3},?{3,?4}?and?{1,?3,?4}. Set?{1,?2,?3,?4}?is not valid, because the third condition isn't satisfied. Set?{1,?4}?satisfies the third condition, but conflicts with the second condition.
題意:RT
思路:樹形DP,dp[u]表示以u(píng)為根,且它的所有子樹的點(diǎn)v的權(quán)值都不超過它,且滿足 w[u]-w[v]<=d 的方案數(shù)
? ? ? ? ? ? 對(duì)于每個(gè)點(diǎn)為根這樣算一遍就好了,注意減去算重的情況,即相鄰多個(gè)點(diǎn)的權(quán)值相等,可以用點(diǎn)的代號(hào)去重(即規(guī)定只能從代號(hào)大的往小的DP)

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

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

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

The key to keep up with HTML standards and best practices is to do it intentionally rather than follow it blindly. First, follow the summary or update logs of official sources such as WHATWG and W3C, understand new tags (such as) and attributes, and use them as references to solve difficult problems; second, subscribe to trusted web development newsletters and blogs, spend 10-15 minutes a week to browse updates, focus on actual use cases rather than just collecting articles; second, use developer tools and linters such as HTMLHint to optimize the code structure through instant feedback; finally, interact with the developer community, share experiences and learn other people's practical skills, so as to continuously improve HTML skills.

The reason for using tags is to improve the semantic structure and accessibility of web pages, make it easier for screen readers and search engines to understand page content, and allow users to quickly jump to core content. Here are the key points: 1. Each page should contain only one element; 2. It should not include content that is repeated across pages (such as sidebars or footers); 3. It can be used in conjunction with ARIA properties to enhance accessibility. Usually located after and before, it is used to wrap unique page content, such as articles, forms or product details, and should be avoided in, or in; to improve accessibility, aria-labeledby or aria-label can be used to clearly identify parts.

To create a basic HTML document, you first need to understand its basic structure and write code in a standard format. 1. Use the declaration document type at the beginning; 2. Use the tag to wrap the entire content; 3. Include and two main parts in it, which are used to store metadata such as titles, style sheet links, etc., and include user-visible content such as titles, paragraphs, pictures and links; 4. Save the file in .html format and open the viewing effect in the browser; 5. Then you can gradually add more elements to enrich the page content. Follow these steps to quickly build a basic web page.

To create an HTML checkbox, use the type attribute to set the element of the checkbox. 1. The basic structure includes id, name and label tags to ensure that clicking text can switch options; 2. Multiple related check boxes should use the same name but different values, and wrap them with fieldset to improve accessibility; 3. Hide native controls when customizing styles and use CSS to design alternative elements while maintaining the complete functions; 4. Ensure availability, pair labels, support keyboard navigation, and avoid relying on only visual prompts. The above steps can help developers correctly implement checkbox components that have both functional and aesthetics.

To reduce the size of HTML files, you need to clean up redundant code, compress content, and optimize structure. 1. Delete unused tags, comments and extra blanks to reduce volume; 2. Move inline CSS and JavaScript to external files and merge multiple scripts or style blocks; 3. Simplify label syntax without affecting parsing, such as omitting optional closed tags or using short attributes; 4. After cleaning, enable server-side compression technologies such as Gzip or Brotli to further reduce the transmission volume. These steps can significantly improve page loading performance without sacrificing functionality.

HTMLhasevolvedsignificantlysinceitscreationtomeetthegrowingdemandsofwebdevelopersandusers.Initiallyasimplemarkuplanguageforsharingdocuments,ithasundergonemajorupdates,includingHTML2.0,whichintroducedforms;HTML3.x,whichaddedvisualenhancementsandlayout

It is a semantic tag used in HTML5 to define the bottom of the page or content block, usually including copyright information, contact information or navigation links; it can be placed at the bottom of the page or nested in, etc. tags as the end of the block; when using it, you should pay attention to avoid repeated abuse and irrelevant content.

ThetabindexattributecontrolshowelementsreceivefocusviatheTabkey,withthreemainvalues:tabindex="0"addsanelementtothenaturaltaborder,tabindex="-1"allowsprogrammaticfocusonly,andtabindex="n"(positivenumber)setsacustomtabbing
