博客
关于我
1118 Birds in Forest
阅读量:424 次
发布时间:2019-03-06

本文共 3465 字,大约阅读时间需要 11 分钟。

Some scientists took pictures of thousands of birds in a forest. Assume that all the birds appear in the same picture belong to the same tree. You are supposed to help the scientists to count the maximum number of trees in the forest, and for any pair of birds, tell if they are on the same tree.

Input Specification:

Each input file contains one test case. For each case, the first line contains a positive number N (≤) which is the number of pictures. Then N lines follow, each describes a picture in the format:

K B​1​​ B​2​​ ... B​K​​

where K is the number of birds in this picture, and B​i​​'s are the indices of birds. It is guaranteed that the birds in all the pictures are numbered continuously from 1 to some number that is no more than 1.

After the pictures there is a positive number Q (≤) which is the number of queries. Then Q lines follow, each contains the indices of two birds.

Output Specification:

For each test case, first output in a line the maximum possible number of trees and the number of birds. Then for each query, print in a line Yes if the two birds belong to the same tree, or No if not.

Sample Input:

43 10 1 22 3 44 1 5 7 83 9 6 4210 53 7
 

Sample Output:

2 10YesNo

 

题意:

  给出一组图画,问画中有几棵树,几只鸟,同一组画中的鸟在同一棵树上。

思路:

  这道题用到了并查集的知识,并查集中有两个重要的函数

1 void findFather(int x) { 2     int a = x; 3     while (x != fa[x]) { 4         x = fa[x]; 5     } 6     while (a != fa[a]) {       // 路径压缩 7         int z = a; 8         a = fa[a]; 9         fa[z] = x;10     }11     return x;12 }

  这个函数是用来寻找某个节点的祖先结点的

1 void Union(int x, int y) {2     int faA = findFather(x);3     int faB = findFather(y);4     if (faA != faB) fa[faA] = faB;5 }    6

  用来合并两个不同的子集。

  


  首先,我们要初始化fa数组,使每个结点的祖先结点是其本身。 

  然后要做的就是将同一副画中的每一个结点通过Union函数合并到一个集合中。

  用exist数组来存储结点是否存在。cnt数组来存储以某一个节点为祖先结点的集合中节点的个数。

 

Code:

1 #include 
2 3 using namespace std; 4 5 const int maxn = 10005; 6 vector
fa(10005); 7 8 int findFather(int x) { 9 int a = x;10 while (x != fa[x]) {11 x = fa[x];12 }13 while (a != fa[a]) {14 int z = a;15 a = fa[a];16 fa[z] = x;17 }18 return x;19 }20 21 void Union(int x, int y) {22 int faX = findFather(x);23 int faY = findFather(y);24 if (faX != faY) fa[faY] = faX;25 }26 27 int main() {28 int n;29 cin >> n;30 31 for (int i = 0; i < maxn; ++i) {32 fa[i] = i;33 }34 35 int k, id, m;36 vector
exist(10005, false);37 vector
cnt(10005, 0);38 int numTrees = 0;39 int numBirds = 0;40 for (int i = 0; i < n; ++i) {41 cin >> k >> id;42 exist[id] = true;43 for (int j = 1; j < k; ++j) {44 cin >> m;45 exist[m] = true;46 Union(id, m);47 }48 }49 for (int i = 1; i < maxn; ++i) {50 if (exist[i]) {51 int root = findFather(i);52 cnt[root]++;53 }54 }55 for (int i = 1; i < maxn; ++i) {56 if (exist[i] && cnt[i] > 0) {57 numTrees++;58 numBirds += cnt[i];59 }60 }61 cout << numTrees << " " << numBirds << endl;62 int querys;63 cin >> querys;64 for (int i = 0; i < querys; ++i) {65 int bird1, bird2;66 cin >> bird1 >> bird2;67 if (findFather(bird1) == findFather(bird2))68 cout << "Yes" << endl;69 else70 cout << "No" << endl;71 }72 return 0;73 }

 

参考:

 

转载地址:http://antuz.baihongyu.com/

你可能感兴趣的文章
Mysql 数据库InnoDB存储引擎中主要组件的刷新清理条件:脏页、RedoLog重做日志、Insert Buffer或ChangeBuffer、Undo Log
查看>>
mysql 数据库备份及ibdata1的瘦身
查看>>
MySQL 数据库备份种类以及常用备份工具汇总
查看>>
mysql 数据库存储引擎怎么选择?快来看看性能测试吧
查看>>
MySQL 数据库操作指南:学习如何使用 Python 进行增删改查操作
查看>>
MySQL 数据库的高可用性分析
查看>>
Mysql 数据库重置ID排序
查看>>
Mysql 数据类型一日期
查看>>
MySQL 数据类型和属性
查看>>
mysql 敲错命令 想取消怎么办?
查看>>
Mysql 整形列的字节与存储范围
查看>>
mysql 断电数据损坏,无法启动
查看>>
MySQL 日期时间类型的选择
查看>>
Mysql 时间操作(当天,昨天,7天,30天,半年,全年,季度)
查看>>
MySQL 是如何加锁的?
查看>>
MySQL 是怎样运行的 - InnoDB数据页结构
查看>>
mysql 更新子表_mysql 在update中实现子查询的方式
查看>>
MySQL 有什么优点?
查看>>
mysql 权限整理记录
查看>>
mysql 权限登录问题:ERROR 1045 (28000): Access denied for user ‘root‘@‘localhost‘ (using password: YES)
查看>>