Exer12_29.cpp

#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <algorithm>
using std::cout;
using std::cin;
using std::endl;
using std::ifstream;
using std::istringstream;
using std::string;
using std::vector;
using std::map;
using std::set;
vector<string>::size_type query(ifstream &infile, const string &query_word)
{
    string str;
    vector<string> text;
    vector<string>::size_type occur_line = 0, cnt = 0;
    map<string, set<vector<string>::size_type>> word_line;
    while(getline(infile, str))
    {
        text.push_back(str);
        string word;
        istringstream istrm_line(str);
        while(istrm_line >> word)
            word_line[word].insert(occur_line);
        ++occur_line;
    }
    auto find_rst = word_line.find(query_word);
    if(find_rst != word_line.end())
    {
        for(auto iter = find_rst->second.cbegin(); iter != find_rst->second.cend(); ++iter)
        {
            string output_line = text[*iter];
            istringstream is(output_line);
            vector<string> line_breakup;
            string out_word;
            while(is >> out_word)
                line_breakup.push_back(out_word);
            cnt += count(line_breakup.cbegin(), line_breakup.cend(), query_word);
            cout << "(line " << *iter << ") " << output_line << endl;
        }
    }
    return cnt;
}
int main(int argc, char* argv[])
{
    if(argc != 2 && argc != 3)
        return -1;
    do
    {
        ifstream in(argv[1]);
        cout << "enter word to look for, or q to quit: ";
        string s;
        if(!(cin >> s) || s == "q")
            break;
        else
        {
            auto cnt = query(in, s);
            cout << "element occurs " << cnt << " times" << endl;
        }
    }while(true);
    return 0;
}