Browser Caching
Browser Caching
题目来源：http://hihocoder.com/contest/mstest2015dec1/problem/1
时间限制:1000ms
单点时限:10000ms
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代码如下：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
public class Main
{
public static void main(String[] args)
{
int n = 0;
int m = 0;
String s = "";
// 包装输入流
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String temp = "";
try
{
// 读取第一行
temp = br.readLine();
}
catch (IOException e1)
{
// TODO Auto-generated catch block
e1.printStackTrace();
}
// br.readLine()将“n m”以字符串读入，因此需要再转换城数字
n = Integer.parseInt(temp.substring(0, temp.indexOf(" ")));
m = Integer.parseInt(temp.substring(temp.indexOf(" ") + 1,
temp.length()));
HashMap
map = new HashMap
(); for (int i = 0; i < n; i++) { try { s = br.readLine(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } // 如果map为空，则将s加入map，输出Internet if (map.isEmpty()) { map.put(s, (Integer) 1); System.out.println("Internet"); } else { // 如果map不为空，则判断map中是否已包含s // 如果已包含，则将value值更新，输出Cache if (map.containsKey(s)) { map.put(s, map.get(s) + (Integer) 1); System.out.println("Cache"); } else { // 如果map不包含s，则判断map是否已满 // 如果未满，则将s加入到map中，输出Internet if (map.size() < m) { map.put(s, (Integer) 1); System.out.println("Internet"); } else { // 如果已满，则遍历map，找出value值最小的元素， // 将此key-value删除，添加s，输出Internet int min = n; String st = ""; for (Object key : map.keySet()) { if (min > map.get(key)) { min = map.get(key); st = (String) key; } } @SuppressWarnings("unused") Object temp1 = map.remove(st); map.put(s, (Integer) 1); System.out.println("Internet"); } } } } } }