2024每日刷题（187）

Leetcode—1242. 多线程网页爬虫

实现代码

/*** // This is the HtmlParser's API interface.* // You should not implement it, or speculate about its implementation* class HtmlParser {*   public:*     vector<string> getUrls(string url);* };*/
class Solution {
public:vector<string> crawl(string startUrl, HtmlParser htmlParser) {queue<string> q{{startUrl}};unordered_set<string> ust{{startUrl}};string hostname = getHostName(startUrl);vector<thread> threads;const int nthreads = std::thread::hardware_concurrency();mutex mtx;condition_variable cv;auto t = [&] {while(true) {unique_lock<mutex> lock(mtx);cv.wait_for(lock, 30ms, [&]() {return q.size();});if(q.empty()) {return;}auto cur = q.front();q.pop();lock.unlock();vector<string> urls = htmlParser.getUrls(cur);lock.lock();for(const string& url: urls) {if(ust.contains(url)) {continue;}if(url.find(hostname) != string::npos) {ust.insert(url);q.push(url);}}lock.unlock();cv.notify_all();}};for(int i = 0; i < nthreads; i++) {threads.emplace_back(t);}for(auto& thread: threads) {thread.join();}return {ust.begin(), ust.end()};}
private:string getHostName(string& s) {int firstIdx = s.find_first_of('/');int thirdIdx = s.find_first_of('/', firstIdx + 2);return s.substr(firstIdx + 2, thirdIdx - firstIdx - 2);}
};

运行结果

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