文件

#include <iostream>
#include <string>
#include <vector>
#include <memory>
#include <fstream>
#include <set>
#include <map>
#include <sstream>

class QueryResult;
std::string make_plural(size_t ctr, const std::string& word, const std::string& ending);

class TextQuery {
public:
    using line_no = std::vector<std::string>::size_type;
    TextQuery(std::ifstream&);
    QueryResult query(const std::string&) const;
private:
    std::shared_ptr<std::vector<std::string>> file;  // 输入文件
    std::map<std::string, std::shared_ptr<std::set<line_no>>> wm;
};

class QueryResult {
    friend std::ostream& print(std::ostream&, const QueryResult&);
public:
    QueryResult(std::string s, std::shared_ptr<std::set<TextQuery::line_no>> p, 
    std::shared_ptr<std::vector<std::string>> f) : sought(s), lines(p), file(f) {}
private:
    std::string sought;  // 查询的词
    std::shared_ptr<std::set<TextQuery::line_no>> lines;
    std::shared_ptr<std::vector<std::string>> file;
};


// 读入行号并建立单词到行号的映射
TextQuery::TextQuery(std::ifstream& is) : file(new std::vector<std::string>) {
    std::string text;
    while (getline(is, text)) {
        file->push_back(text);  // 保存此行文本
        int n = file->size() - 1;  // 行号
        std::istringstream line(text);
        std::string word;
        while (line >> word) {
            auto& lines = wm[word];
            if (lines == nullptr) {
                lines.reset(new std::set<line_no>);
            }
            lines->insert(n);
        }
    }
}

QueryResult TextQuery::query(const std::string& sought) const {
    // 如果未找到，返回一个空的 set
    static std::shared_ptr<std::set<TextQuery::line_no>> 
    nodata(new std::set<TextQuery::line_no>);

    auto loc = wm.find(sought);
    if (loc != wm.end()) {
        return QueryResult(sought, loc->second, file);
    } else {
        return QueryResult(sought, nodata, file);
    }
}

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 << "(line " << num + 1 << ") " << *(qr.file->begin() + num) << std::endl; 
    }
    return os;
}

std::string make_plural(size_t ctr, const std::string& word, const std::string& ending) {
    return ctr > 1 ? word + ending : word;
}

void runQueries(std::ifstream& infile) {
    TextQuery tq(infile);
    
    while (true) {
        std::cout << "enter word to look for, or q to quit" << std::endl;
        std::string s;
        if (!(std::cin >> s) || s == "q") {
            break;
        }
        print(std::cout, tq.query(s)) << std::endl;
    }
}

int main() {
    std::string fileName;
    std::cin >> fileName;

    std::ifstream file;
    file.open(fileName);
    
    if (file.is_open()) {
        runQueries(file);
        file.close();
    } else {
        std::cout << "Failed to open the file." << std::endl;
    }

    return 0;
}