hiho一下第六十二周Browser Caching

最新推荐文章于 2019-10-07 15:22:30 发布

原创最新推荐文章于 2019-10-07 15:22:30 发布 · 490 阅读

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本文介绍了一种模拟浏览器缓存行为的算法实现。通过设定缓存大小和访问历史记录，该算法可以判断每次请求是从缓存还是互联网获取页面。文章包含了一个具体的示例和源代码，展示了如何使用最近最少使用（LRU）策略来更新和查询缓存。

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

这道题真不赖，自己还是看了解题思路和题http://hihocoder.com/discuss/question/2154解搞定的

#include<iostream>
#include<cstdio>
#include<cstring>
#include<map>
#include<algorithm>
using namespace std;
#define N 200005
map<string,int> lastVisit;
string a[N];
int main()
{
    int n,m;
    scanf("%d%d",&n,&m);
    int start=1;
    int cacheCnt=0;
    for(int i=1;i<=n;i++)
    {
        cin>>a[i];
        if(lastVisit[a[i]]>=start && lastVisit[a[i]]<i)  //这里只需<i就行了，
            printf("Cache\n");
        else
        {
            printf("Internet\n");
            cacheCnt++;
            if(cacheCnt>m)
            {
                start=start+1;
            }
        }
        lastVisit[a[i]]=i;
        while(lastVisit[a[start]]!=start)
            start++;
    }
    return 0;
}