main.cpp

C++ primary中的TEXTQUERY程序

#include <iostream>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <fstream>
#include <cctype>
#include <cstring>
#include <sstream>
#include <stdexcept>
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;
};

ifstream& open_file(ifstream &in ,const string &file)
{//打开并检查输入文件
	in.close();
	in.clear();
	in.open(file.c_str());
	return in;
}

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 << "\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;
	}
}


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

void TextQuery::build_map()
{//建立单词map容器
	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);
	}
}

set<TextQuery::line_no> //支持查询
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;
}

string TextQuery::text_line(line_no line) const
{
	if(line < lines_of_text.size())
		return lines_of_text[line];
	throw out_of_range("line number out of range");
}

int main(int argc, char **argv)
{
	ifstream infile;
	if(argc < 2 || !open_file(infile,argv[1]))
	{
		cerr << "No input file !" << endl;
		system("PAUSE");
		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);
	}
	system("PAUSE");
    return EXIT_SUCCESS;
}