【hihoCoder】#1086: Browser Caching (微软笔试题)

#1086 : Browser Caching

时间限制:10000ms
单点时限:1000ms
内存限制:256MB

描述

When you browse the Internet, browser usually caches some documents to reduce the time cost of fetching them from remote servers. Let's consider a simplified caching problem. Assume the
size of browser's cache can store M pages. When user visits some URL, browser will search it in the cache first. If the page is already cached browser will fetch it from the cache, otherwise browser will fetch it from the Internet and store it in the cache.
When the cache is full and browser need to store a new page, the least recently visited page will be discarded.
Now, given a user's browsing history please tell us where did browser fetch the pages, from the cache or the Internet? At the beginning browser's cache is empty.

输入

Line 1: Two integers N(1 <= N <= 20000) and M(1 <= M <= 5000). N is the number of pages visited and M is the cache size.
Line 2~N+1: Each line contains a string consisting of no more than 30 lower letters, digits and dots('.') which is the URL of the page. Different URLs always lead to different pages. For
example www.bing.com and bing.com are considered as different pages by browser.

输出

Line 1~N: For each URL in the input, output "Cache" or "Internet".

提示

Pages in the cache before visiting 1st URL [null, null]
Pages in the cache before visiting 2nd URL [www.bing.com(1), null]
Pages in the cache before visiting 3rd URL [www.bing.com(1), www.microsoft.com(2)]
Pages in the cache before visiting 4th URL [www.bing.com(1), www.microsoft.com(3)]
Pages in the cache before visiting 5th URL [windows.microsoft.com(4), www.microsoft.com(3)]
The number in parentheses is the last visiting timestamp of the page.

样例输入

5 2
www.bing.com
www.microsoft.com
www.microsoft.com
windows.microsoft.com
www.bing.com

样例输出

Internet
Internet
Cache
Internet

Internet

import java.util.LinkedList;
import java.util.Scanner;

public class Main {
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
// URL的数量
int urlNum = in.nextInt();
// Cache的容量
int cacheCapacity = in.nextInt();
// 验证输入的合法性
if(cacheCapacity>0 && urlNum>0){
// 使用链式存储结构来存储URL，插入、删除操作方便
LinkedList<String> cacheList = new LinkedList<String>();
// 读取第一行，为了转到下一行
in.nextLine();
// 逐行遍历URL
for(int i=0; i<urlNum; i++){
// 读取当前URL
String url = in.nextLine();
// 判断该URL是否存在于缓存cache中
if(cacheList.contains(url)){
// 存在，则先将缓存cache中该URL的节点删除
cacheList.remove(url);
// 打印结果
System.out.println("Cache");
}
else{
// 不存在，则先判断缓存是否已满
if(cacheList.size()==cacheCapacity){
// 缓存已满，则将队首的元素弹出
cacheList.poll();
}
// 打印结果
System.out.println("Internet");
}
// 最后，将当前最新的URL入队
cacheList.offer(url);
}
}
// 关闭输入流
in.close();
}
}