C++自学笔记_文本查询程序_《C++ Primer》

#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <fstream>
#include <sstream>
#include <stdexcept>

using namespace std;

class TextQuery{
public:
    typedef vector<string>::size_type line_no;
    void read_file(ifstream &is){
        store_file(is);
        build_map();
    }
    set<line_no> run_query(const string&) const;
    string text_line(line_no) const;
private:
    void store_file(ifstream &);
    void build_map();
    vector<string> lines_of_text;
    map<string,set<line_no> >word_map;
};

/*存储输入文件*/
void TextQuery::store_file(ifstream &is){
    string textline;
    while(getline(is,textline)){
        lines_of_text.push_back(textline);
    }
}

/*建立map容器*/
void TextQuery::build_map(){
    for(line_no line_num=0;line_num!=lines_of_text.size();++line_num){
        istringstream line(lines_of_text[line_num]);
        string word;
        while(line>>word){
            word_map[word].insert(line_num);
        }
    }
}

/*支持查询*/
set<TextQuery::line_no> TextQuery::run_query(const string &query_word) const{
    map<string,set<line_no> >::const_iterator loc=word_map.find(query_word);
    if(loc==word_map.end())
        return set<line_no>();
    else
        return loc->second;
}

/*run_query返回值的使用*/
string TextQuery::text_line(line_no line) const{
    if(line<lines_of_text.size())
        return lines_of_text[line];
    else
        throw out_of_range("line number out of range");
}

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

void print_results(const set<TextQuery::line_no>& locs,const string& sought,const TextQuery &file){
    typedef set<TextQuery::line_no> line_nums;
    line_nums::size_type size=locs.size();
    cout<<"\n"<<sought<<" occurs "<<size<<make_plural(size," time","s")<<endl;
    line_nums::const_iterator it=locs.begin();
    for( ;it!=locs.end();++it){
        cout<<"\t(line "<<(*it)+1<<") "<<file.text_line(*it)<<endl;
    }
}

int main()
{
    ifstream infile;
    cout<<"enter a file path to query: ";
    string fileName;
    getline(cin,fileName);
    infile.open(fileName.c_str());
    TextQuery tq;
    tq.read_file(infile);
    while(true){
        cout<<endl<<"enter a word to look for,or q to quit: ";
        string str;
        cin>>str;
        if(!cin||str=="q")
            break;
        set<TextQuery::line_no> locs=tq.run_query(str);
        print_results(locs,str,tq);
    }
    return 0;
}