1 Our program will read a file specified by the user and then allow the user to
2 search the file for words that might occur in it. The result of a query will be
3 the number of times the word occurs and a list of lines on which
4 it appears. If a word occurs more than once on the same line,
5 our program should be smart enough to display that line only once.
6 Lines should be displayed in ascending orderthat is,
7 line 7 should be displayed before line 9, and so on.

#ifndef __TEXTQUERY_H__
#define __TEXTQUERY_H__#include <iostream>
#include <istream>
#include <fstream>
#include <vector>
#include <map>
#include <set>
#include <utility>
#include <string>typedef std::vector<std::string>::size_type line_no;class TextQuery {public:// interface: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:// utility functions used by read_filevoid store_file(std::ifstream&);void build_map(); // associate each word with a set of line numbers// remember the whole input filestd::vector<std::string> lines_of_text;// map word to set of the lines on which it occursstd::map< std::string, std::set<line_no> > word_map;
};#endif

// opens in binding it to the given file
ifstream& open_file(ifstream &in, const string &file)
{in.close();     // close in case it was already openin.clear();     // clear any existing errors// if the open fails, the stream will be in an invalid statein.open(file.c_str()); // open the file we were givenreturn in; // condition state is good if open succeeded
}

#include "TextQuery.h"define    EXIT_FAILURE    -1using namespace std;int main(int argc, char *argv[])
{// open the file from which user will quer words
    ifstream infile;if(argc < 2 || !open_file(infile, argv[1])){cerr << "No input file!" << endl;return EXIT_FAILURE;}TextQuery tq;tq.read_file(infile);// prompt for a word to file and print resultwhile(true){cout << "Enter word to look for(or Q/q to Quit): \n" ;string str;cin >> str;// stop if hit eof on input or a 'Q' is entered if(!cin || str == "Q" || str == "q")break;// get tje set of line numbers on which this word appearsset<line_no> locs = tq.run_query(str);// print count an all occurrences, if any
        print_results(locs, str, tq);}return 0;
}

// return plural version of word if ctr isn't 1
string make_plural(size_t ctr, const string &word,const string &ending)
{return (ctr == 1) ? word : word + ending;
}

void print_results(const set<line_no>& locs, const string& sought, const TextQuery& file)
{// if the word was found, then print count and all occurrencestypedef set<line_no> line_nums;line_nums::size_type size = locs.size();cout << "\n" << sought << " occurs " << size << " "<< make_plural(size, "time", "s") << endl;// print each line in which the word appearedline_nums::const_iterator it = locs.begin();for(; it != locs.end(); ++it){// don't confound user with text lines starting at 0cout << "\t(line" << (*it) +1 << ")" << file.text_line(*it) << endl;}
}

#include "TextQuery.h"
#include <stdexcept>
#include <sstream>using namespace std;set<line_no> TextQuery::run_query(const string &query_word) const
{// must use find and not subscript he map directly// to avoid adding words to word_mapmap< string, set<line_no> >::const_iteratorloc = word_map.find(query_word);if(loc == word_map.end()){// not found, return empty setreturn set<line_no>(); }else{// fectch and return set of line numbers for this wordreturn 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");
}// utility functions used by read_file
void TextQuery::store_file(ifstream &is)
{string textline;while (getline(is, textline))lines_of_text.push_back(textline);
}// associate each word with a set of line numbers
void TextQuery::build_map()
{// process each line from the input vectorfor (line_no line_num = 0; line_num != lines_of_text.size(); ++line_num) {// we'll use line to read the text a word at a time
        istringstream line(lines_of_text[line_num]);string word;while (line >> word){// add this line number to the set;// subscript will add word to the map if it's not already there
            word_map[word].insert(line_num);}}
}