Exer11_03_04.cpp

#include <iostream>
#include <fstream>
#include <string>
#include <cstddef>
#include <cctype>
#include <map>
#include <set>
using std::cout;
using std::endl;
using std::ifstream;
using std::string;
using std::size_t;
using std::map;
using std::set;
int main(int argc, char *argv[])
{
    if(argc != 2)
        return -1;
    ifstream is(argv[1]);
    map<string, size_t> word_count; // empty map from string to size_t
    string word;
    while(is >> word)
    {
        for(auto &c : word)
            c = tolower(c); // convert all words to upper case
        ++word_count[word];
    }
    for(const auto &w : word_count)
        // print the result
        cout << w.first << " occurs " << w.second
             << ((w.second > 1) ? " times" : " time") << endl;
    return 0;
}