首页 / HTML / CodeforcesRound#245(Div.2)D（树的性质+状压+dfs）_html/css_WEB-ITnose

CodeforcesRound#245(Div.2)D（树的性质+状压+dfs）_html/css_WEB-ITnose

内容导读

互联网集市收集整理的这篇技术教程文章主要介绍了CodeforcesRound#245(Div.2)D（树的性质+状压+dfs）_html/css_WEB-ITnose，小编现在分享给大家，供广大互联网技能从业者学习和参考。文章包含2090字，纯文字阅读大概需要3分钟。

内容图文

E. Guess the Tree

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

Iahub and Iahubina went to a picnic in a forest full of trees. Less than 5 minutes passed before Iahub remembered of trees from programming. Moreover, he invented a new problem and Iahubina has to solve it, otherwise Iahub won't give her the food.

Iahub asks Iahubina: can you build a rooted tree, such that

  • each internal node (a node with at least one son) has at least two sons;
  • node i has ci nodes in its subtree?

    • Iahubina has to guess the tree. Being a smart girl, she realized that it's possible no tree can follow Iahub's restrictions. In this way, Iahub will eat all the food. You need to help Iahubina: determine if there's at least one tree following Iahub's restrictions. The required tree must contain n nodes.

    Input

    The first line of the input contains integer n (1?≤?n?≤?24). Next line contains n positive integers: the i-th number represents ci (1?≤?ci?≤?n).

    Output

    Output on the first line "YES" (without quotes) if there exist at least one tree following Iahub's restrictions, otherwise output "NO" (without quotes).

    Sample test(s)

    input 

    41 1 1 4

    output 

    YES

    input 

    51 1 5 2 1

    output 

    NO

    题意：RT


    思路：首先注意，根据每个点至少有两个孩子这个性质可以知道，为1的点的数量一定会>=n/2


    所以24个点的状态就减少为12个点的状态，敲好可以状压


    只考虑不为1的点，先按降序排序，然后一个一个选孩子，如果已经轮到i来选孩子，先检查它自己有没有被前面的点选为孩子，


    如果没有选，则不需要继续了，因为它不可能有父亲了


    如果选了，则继续为i选2个或以上的孩子，选过的点标记一下就可以了


    整个过程用递归算就可以了

    内容总结

    以上是互联网集市为您收集整理的CodeforcesRound#245(Div.2)D（树的性质+状压+dfs）_html/css_WEB-ITnose全部内容，希望文章能够帮你解决CodeforcesRound#245(Div.2)D（树的性质+状压+dfs）_html/css_WEB-ITnose所遇到的程序开发问题。 如果觉得互联网集市技术教程内容还不错，欢迎将互联网集市网站推荐给程序员好友。

    内容备注

    版权声明：本文内容由互联网用户自发贡献，该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 gblab@vip.qq.com 举报，一经查实，本站将立刻删除。

    内容手机端

    扫描二维码推送至手机访问。

    本文链接：https://qyyshop.com/info/399513.html

    来源：【匿名】