C++11: Dynamic Memory

来源：互联网发布：新歌2016网络吐槽红歌编辑：程序博客网时间：2024/05/22 15:43

#include <vector>#include <memory>#include <string>#include <map>#include <set>#include <iostream>#include <sstream>#include <fstream>class QueryResult;class TextQuery {public:        using line_no = std::vector<std::string>::size_type;        TextQuery(std::ifstream&);        QueryResult query(const std::string &);private:        std::shared_ptr<std::vector<std::string>> file;        std::map<std::string, std::shared_ptr<std::set<line_no>>> wm;};std::ostream& print(std::ostream &, const QueryResult &);class QueryResult {        friend std::ostream& print(std::ostream &, const QueryResult &);public:        using line_no = std::vector<std::string>::size_type;        QueryResult(std::string s,                    std::shared_ptr<std::set<line_no>> p,                    std::shared_ptr<std::vector<std::string>> f) :                sought(s), lines(p), file(f) { }private:        std::string sought;        std::shared_ptr<std::set<line_no>> lines;        std::shared_ptr<std::vector<std::string>> file;};void runQueries(std::ifstream &is){        TextQuery tq(is);        while (true) {                std::cout << "enter word to look for, or q to quit: ";                std::string s;                if (!(std::cin >> s) || s == "q") break;                print(std::cout, tq.query(s)) << std::endl;        }}int main(){        std::ifstream is("data.dat");        runQueries(is);        return 0;}TextQuery::TextQuery(std::ifstream &is) : file(new std::vector<std::string>){        std::string text;        while (std::getline(is, text)) {                file->push_back(text);                int n = file->size() - 1;                std::istringstream line(text);                std::string word;                while (line >> word) {                        auto &lines = wm[word];                        if (!lines) {                                lines.reset(new std::set<line_no>);                        }                        lines->insert(n);                }        }}QueryResult TextQuery::query(const std::string &word){        static std::shared_ptr<std::set<line_no>> nodata(new std::set<line_no>);        auto loc = wm.find(word);        if (loc == wm.end()) {                return QueryResult(word, nodata, file);        } else {                return QueryResult(word, loc->second, file);        }}std::string make_plural(std::size_t ctr, const std::string &word, const std::string &ending){        return (ctr > 0) ? word + ending : word;}std::ostream& print(std::ostream &os, const QueryResult &qr){        os << qr.sought << " occurs " << qr.lines->size() << " "           << make_plural(qr.lines->size(), "time", "s") << std::endl;        for (auto num : *qr.lines) {                os << "\t(line " << num + 1 << ") "                   << *(qr.file->begin() + num) << std::endl;        }        return os;}

/* clang++ xx.cpp -std=c++11** Apple LLVM version 7.0.2 (clang-700.1.81)** Target: x86_64-apple-darwin15.2.0** Thread model: posix*/// C++ primer 5th: Using the Library: A Text-Query Program(p484)

0 0