Wordcount in C++
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#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <algorithm>
#include <map>
#include <locale>
using std::cerr;
using std::endl;
template <typename Pair> bool greater_second(const Pair& p1, const Pair& p2)
{
return p1.second > p2.second;
}
std::locale loc("");
typedef std::vector<std::pair<std::string, int> > word_list;
typedef std::map<std::string, int> word_map;
static bool get_word(std::istream& input, std::string& word)
{
char c;
while (input && input.get(c) && !std::isalpha(c, loc));
if (!input)
{
return false;
}
word.clear();
while (std::isalpha(c, loc))
{
word.push_back(std::tolower(c, loc));
input.get(c);
}
input.putback(c);
return true;
}
static void build_concordance(std::istream& input, word_map& concordance)
{
std::string word;
while (get_word(input, word))
{
++concordance[word];
}
}
static void print_top_n(const word_list& list, int n)
{
for (word_list::const_iterator i = list.begin();
i != list.end() && i - list.begin() < n;
++i)
{
std::cout << (*i).first << " " << (*i).second << endl;
}
}
int main(int argc, char const* const *argv)
{
if (argc < 2)
{
cerr << "Usage: " << argv[0] << " <file>" << endl;
return 1;
}
if (argc > 2)
{
cerr << argv[0] << ": too many command-line arguments" << endl;
return 1;
}
std::ifstream input;
try
{
input.open(argv[1]);
}
catch (const std::exception& ex)
{
cerr << argv[0] << " unable to open " << argv[1] << endl;
}
word_map concordance;
build_concordance(input, concordance);
word_list list(concordance.begin(), concordance.end());
std::sort(list.begin(), list.end(), greater_second<word_map::value_type>);
print_top_n(list, 10);
return 0;
}
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