c++ primier 第十章文本查询实例

#include<iostream>#include<fstream>#include<string>#include<sstream>#include<vector>#include<map>#include<set>using namespace std;class TextQuery{public:typedef std::vector<std::string>::size_type line_no;void read_file(std::ifstream &is){store_file(is);build_map();}std::set<line_no> run_query(const std::string&) const;std::string text_line(line_no) const;private:void store_file(std::ifstream &);void build_map();std::vector<std::string> lines_of_text;std::map<std::string,std::set<line_no> >word_map;};void TextQuery::store_file(std::ifstream &is){std::string textline;while(getline(is,textline))lines_of_text.push_back(textline);}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]);std::string word;while(line>>word)word_map[word].insert(line_num);}}set<TextQuery::line_no>TextQuery::run_query(const string &query_word) const{map<string,set<line_no> >::const_iteratorloc = word_map.find(query_word);if(loc == word_map.end())return set<line_no>();elsereturn loc->second;}string TextQuery::text_line(line_no line) const{if(line < lines_of_text.size())return lines_of_text[line];throw std::out_of_range("line number out of range");}string make_plural(size_t 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<<endl<<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;}}ifstream & open_file(ifstream &in , const string &file){in.close();in.clear();in.open(file.c_str());return in;}int main(int argc,char *argv[]){ifstream infile;if(argc<2|| !open_file(infile,argv[1])){cerr<<"No input file!"<<endl;return EXIT_FAILURE;}TextQuery tq;tq.read_file(infile);while(true){cout<<"enter word to look for , or q to quit:";string s;cin>>s;if(!cin || s == "q")break;set<TextQuery::line_no> locs = tq.run_query(s);print_results(locs,s,tq);}return 0;}