codeforces 987 D. Fair
2 seconds
512 megabytes
standard input
standard output
Some company is going to hold a fair in Byteland. There are $$$n$$$ towns in Byteland and $$$m$$$ two-way roads between towns. Of course, you can reach any town from any other town using roads.
There are $$$k$$$ types of goods produced in Byteland and every town produces only one type. To hold a fair you have to bring at least $$$s$$$ different types of goods. It costs $$$d(u,v)$$$ coins to bring goods from town $$$u$$$ to town $$$v$$$ where $$$d(u,v)$$$ is the length of the shortest path from $$$u$$$ to $$$v$$$. Length of a path is the number of roads in this path.
The organizers will cover all travel expenses but they can choose the towns to bring goods from. Now they want to calculate minimum expenses to hold a fair in each of $$$n$$$ towns.
There are $$$4$$$ integers $$$n$$$, $$$m$$$, $$$k$$$, $$$s$$$ in the first line of input ($$$1 \le n \le 10^{5}$$$, $$$0 \le m \le 10^{5}$$$, $$$1 \le s \le k \le min(n, 100)$$$) — the number of towns, the number of roads, the number of different types of goods, the number of different types of goods necessary to hold a fair.
In the next line there are $$$n$$$ integers $$$a_1, a_2, \ldots, a_n$$$ ($$$1 \le a_{i} \le k$$$), where $$$a_i$$$ is the type of goods produced in the $$$i$$$-th town. It is guaranteed that all integers between $$$1$$$ and $$$k$$$ occur at least once among integers $$$a_{i}$$$.
In the next $$$m$$$ lines roads are described. Each road is described by two integers $$$u$$$ $$$v$$$ ($$$1 \le u, v \le n$$$, $$$u \ne v$$$) — the towns connected by this road. It is guaranteed that there is no more than one road between every two towns. It is guaranteed that you can go from any town to any other town via roads.
Print $$$n$$$ numbers, the $$$i$$$-th of them is the minimum number of coins you need to spend on travel expenses to hold a fair in town $$$i$$$. Separate numbers with spaces.
5 5 4 3
1 2 4 3 2
1 2
2 3
3 4
4 1
4 5
2 2 2 2 3
7 6 3 2
1 2 3 3 2 2 1
1 2
2 3
3 4
2 5
5 6
6 7
1 1 1 2 2 1 1
Let's look at the first sample.
To hold a fair in town $$$1$$$ you can bring goods from towns $$$1$$$ ($$$0$$$ coins), $$$2$$$ ($$$1$$$ coin) and $$$4$$$ ($$$1$$$ coin). Total numbers of coins is $$$2$$$.
Town $$$2$$$: Goods from towns $$$2$$$ ($$$0$$$), $$$1$$$ ($$$1$$$), $$$3$$$ ($$$1$$$). Sum equals $$$2$$$.
Town $$$3$$$: Goods from towns $$$3$$$ ($$$0$$$), $$$2$$$ ($$$1$$$), $$$4$$$ ($$$1$$$). Sum equals $$$2$$$.
Town $$$4$$$: Goods from towns $$$4$$$ ($$$0$$$), $$$1$$$ ($$$1$$$), $$$5$$$ ($$$1$$$). Sum equals $$$2$$$.
Town $$$5$$$: Goods from towns $$$5$$$ ($$$0$$$), $$$4$$$ ($$$1$$$), $$$3$$$ ($$$2$$$). Sum equals $$$3$$$.
【题意】
$$$n$$$个结点,$$$m$$$条边,$$$s$$$种商品,每个结点含有一种商品,且保证所有商品至少被一个结点包含。对于每个结点,选择至少$$$k$$$个结点,使他们包含至少$$$k$$$种商品,且到该结点的总距离和最小。
【思路】
结点和边的数量为1e5,而商品个数只有100,如果从每个结点出发直到寻找$$$k$$$个商品为止,那么这样做其实并不划算,其原因在于很难决定最近的商品在哪条路上,需要搜索到很深的地方,而且含有相同商品的城市会被反复访问。为了节约时间,可以预先从商品出发进行bfs,那么经过的城市都是最近的,这样处理以后每个城市就知道,自己到每个商品的最近距离,要凑齐$$$k$$$个商品只需要选择前k个最小的距离就行了。
【注意】
这里的bfs需要抽象理解一下,假如对$$$i$$$号商品进行bfs,那么第一步就要直接转移到所有含$$$i$$$的城市,然后就是平常的bfs了,每次扩展1个距离,遍历完所有城市后,每个城市就都有一个获得$$$i$$$的最短距离了。
【代码】
#include<stdio.h>
#include<queue>
#include<memory.h>
#include<algorithm>
#include<vector> using std::queue;
using std::vector;
using std::sort; vector<int> t[];
#define N 100005
vector<int>node[N];
int cost[N][] = { };
int vis[N];
void bfs(int si) {
queue<int>help; int sz = t[si].size();
//将含si的所有城市加入到bfs的第一次转移
for (int i = ; i < sz; ++i) {
int next=t[si][i];
help.push(next);
vis[next] = ;
}
//bfs继续转移
for (int cnt = ; !help.empty();cnt++) {
int sz = help.size();
for (int i = ; i < sz; ++i) {
int next = help.front(); help.pop();
int nsz = node[next].size();
for (int t = ; t < nsz; ++t) {
int pnext = node[next][t];
if (vis[pnext] == )continue;
vis[pnext] = ;
cost[pnext][si] = cnt;
help.push(pnext);
}
}
}
} int main() {
int n, m, s, k;
scanf("%d %d %d %d", &n, &m, &s, &k);
int a0,a1;
for (int i = ; i <= n; ++i) {
scanf("%d", &a0);
t[a0].push_back(i);
}
for (int i = ; i < m; ++i) {
scanf("%d %d", &a0, &a1);
node[a0].push_back(a1);
node[a1].push_back(a0);
}
for (int i = ; i <= s; ++i) {
memset(vis, , sizeof vis);
bfs(i);
}
for (int i = ; i <= n; ++i) {
//排序并选择前k个
sort(cost[i] + , cost[i] + + s);
int sum = ;
for (int t = ; t <= k; ++t)
sum += cost[i][t];
printf("%d ", sum);
}
}
codeforces 987 D. Fair的更多相关文章
- codeforces 897A Scarborough Fair 暴力签到
codeforces 897A Scarborough Fair 题目链接: http://codeforces.com/problemset/problem/897/A 思路: 暴力大法好 代码: ...
- CF 987 D. Fair
D. Fair http://codeforces.com/contest/987/problem/D 题意: n个城镇m条道路,(保证没有重边,两个城镇间可以到达),每个城镇拥有的特产ai(可能多个 ...
- [Codeforces Round 486A] Fair
[题目链接] https://codeforces.com/contest/986/problem/A [算法] 用dist(i,j)表示第i种食物运到第j个城市需要的最小代价 将所有特产为第i中食物 ...
- CodeForces 1084D The Fair Nut and the Best Path
The Fair Nut and the Best Path 题意:求路径上的 点权和 - 边权和 最大, 然后不能存在某个点为负数. 题解: dfs一遍, 求所有儿子走到这个点的最大值和次大值. 我 ...
- CodeForces - 1073D Berland Fair
XXI Berland Annual Fair is coming really soon! Traditionally fair consists of nnbooths, arranged in ...
- Codeforces 987 K预处理BFS 3n,7n+1随机结论题/不动点逆序对 X&Y=0连边DFS求连通块数目
A /*Huyyt*/ #include<bits/stdc++.h> #define mem(a,b) memset(a,b,sizeof(a)) #define pb push_bac ...
- Codeforces 1083E The Fair Nut and Rectangles
Description 有\(N\)个左下定点为原点的矩阵, 每个矩阵\((x_i,~y_i)\)都有一个数\(a_i\)表示其花费. 没有一个矩阵包含另一个矩阵. 现要你选出若干个矩阵, 使得矩阵组 ...
- Codeforces 1083B The Fair Nut and Strings
Description 给定两个由 \('a'\), \('b'\) 组成的字符串 \(a\), \(b\),以及两个整数 \(n\) 和 \(k\) \(n\) 表示字符串 \(a\),\(b\) ...
- Codeforces 987 F - AND Graph
F - AND Graph 思路: 首先,x & (~x) == 0 其次,~x 的 子集 y = ((~x) ^ (1<<k)), 0<= k < n(如果k这一位是 ...
随机推荐
- 优步UBER司机全国各地奖励政策汇总 (4月4日-4月10日)
滴快车单单2.5倍,注册地址:http://www.udache.com/ 如何注册Uber司机(全国版最新最详细注册流程)/月入2万/不用抢单:http://www.cnblogs.com/mfry ...
- 成都Uber优步司机奖励政策(1月11日)
滴快车单单2.5倍,注册地址:http://www.udache.com/ 如何注册Uber司机(全国版最新最详细注册流程)/月入2万/不用抢单:http://www.cnblogs.com/mfry ...
- Java实现邮件发送
概述 Spring Boot下面整合了邮件服务器,使用Spring Boot能够轻松实现邮件发送:整理下最近使用Spring Boot发送邮件和注意事项: Maven包依赖 <depende ...
- React-精华版
现在最热门的前端框架有AngularJS.React.Bootstrap等.自从接触了ReactJS,ReactJs的虚拟DOM(Virtual DOM)和组件化的开发深深的吸引了我,下面来跟我一起领 ...
- Linux命令应用大词典-第39章 网络安全
39.1 rtacct:网络统计工具 39.2 nmap:报告远程主机特征 39.3 tcpdump:实现网络数据采集分析 39.4 iptstate:显示IP表状态表条目 39.5 nstat:监控 ...
- [JSON].value( keyPath )
语法:[JSON].value( keyPath ) 返回:[String | Null] 说明:获取指定键名路径值的字符串格式 示例: Set jsonObj = toJson("{bod ...
- js如何判断客户端是iOS还是Android等移动终端
判断原理:JavaScript是前端开发的主要语言,我们可以通过编写JavaScript程序来判断浏览器的类型及版本.JavaScript判断浏览器类型一般有两种办法,一种是根据各种浏览器独有的属性来 ...
- 并发HashMap的put操作引起死循环
今天研读Java并发容器和框架时,看到为什么要使用ConcurrentHashMap时,其中有一个原因是:线程不安全的HashMap, HashMap在并发执行put操作时会引起死循环,是因为多线程会 ...
- mweb test
目录 Markdown syntax guide and writing on MWeb Philosophy Notice Headers This is an <h1> tag Thi ...
- 基于Kubernetes(k8s)的RabbitMQ 集群
目前,有很多种基于Kubernetes搭建RabbitMQ集群的解决方案.今天笔者今天将要讨论我们在Fuel CCP项目当中所采用的方式.这种方式加以转变也适用于搭建RabbitMQ集群的一般方法.所 ...