12.30.cpp

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

using namespace std;

using line_no = std::vector<std::string>::size_type;

class QueryResult;

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(ifstream &is):file(new vector<string>)
{
	string text;
	while(getline(is,text)){
		file -> push_back(text);
		int n = file -> size() -1;
		istringstream line(text);
		string word;
		while(line >> word){
			auto &lines = wm[word];
			if(!lines)
				lines.reset(new set<line_no>);
			lines -> insert(n);
		}
	}
};

class QueryResult{
	friend std::ostream& print(std::ostream&, const QueryResult&);
	public:
	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;
};


QueryResult TextQuery::query(const string &sought) const{
	static shared_ptr<set<line_no>> nodata(new set<line_no>);
	auto loc = wm.find(sought);
	if(loc == wm.end())
		return QueryResult(sought, nodata, file);
	else
		return QueryResult(sought,loc->second,file);
}

ostream& print(ostream& os, const QueryResult &qr)
{
	os << qr.sought << " occurs " << qr.lines->size() << " times " << endl;
	for(auto num : *qr.lines){
		os << "\t(line " << num + 1 << ")" << *(qr.file->begin() + num) << endl;
	}
	return os;
}


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

int main(int argc, char* argv[])
{
	ifstream in(argv[1]);
	if(in){
		runQueries(in);
	}

	system("pause");
	return 0;
}