CppPrimer-第12章-文本查询程序

定义QueryResult

//
// Created by modao on 2021-01-6//

#ifndef TEXT_QUERY_QUERYRESULT_H
#define TEXT_QUERY_QUERYRESULT_H

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

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;
}
#endif //TEXT_QUERY_QUERYRESULT_H

定义TextQuery

//
// Created by modao on 2021-01-6//

#ifndef TEXT_QUERY_TEXTQUERY_H
#define TEXT_QUERY_TEXTQUERY_H
#include "QueryResult.h"

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;
    std::map<std::string, std::shared_ptr<std::set<line_no>>> wm;
};
TextQuery::TextQuery(std::ifstream &is): file(new std::vector<std::string>) {
    std::string text;
    while(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 &sought) const {
    static std::shared_ptr<std::set<line_no>> nodata(new std::set<line_no>);

    auto loc = wm.find(sought);
    if(loc == wm.end())
        return QueryResult(sought, nodata, file);
    else
        return QueryResult(sought, loc->second, file);
}
#endif //TEXT_QUERY_TEXTQUERY_H

编写main函数

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

#include "TextQuery.h"

void runQueries(std::ifstream &infile){
    TextQuery tq(infile);
    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() {
    //必须使用绝对路径
    std::ifstream file("E:\\clion_workspace\\Text_query\\file.txt");
    runQueries(file);
    return 0;
}

cmake文件

cmake_minimum_required(VERSION 3.12)
project(Text_query)

set(CMAKE_CXX_STANDARD 20)

add_executable(Text_query main.cpp TextQuery.h QueryResult.h)

file.txt文件

abc inad
sd faf
 as
 df
 asfd
  as
  df