find out passwords most frequently used by CSDN users

csdntopk.cpp

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
#include <unordered_map>

int main()
{
    typedef std::unordered_map<std::string, std::size_t> Dict;
    typedef std::vector<std::pair<std::string, std::size_t> > Heap;
    const std::size_t K = 1000;
    const std::size_t Col = 3;
    const char sep[] = "\t ";
    char line[BUFSIZ];
    char *token, *context;
    Dict dict;
    Heap heap;
    while (::fgets(line, BUFSIZ, stdin)) {
        for (std::size_t i = 0; i < Col; ++i) {
            token = ::strtok_s((0 == i) ? line : NULL, sep, &context);
        }
        dict[token] = dict[token] + 1;
    }
    heap.resize(dict.size());
    std::transform(dict.begin(), dict.end(), heap.begin(), [](const Dict::value_type& elem){ return std::make_pair(elem.first, elem.second); });
    std::partial_sort(heap.begin(), heap.begin() + K, heap.end(), [](const Heap::value_type& a, const Heap::value_type& b){ return a.second > b.second; });
    std::for_each(heap.begin(), heap.begin() + K, [](const Heap::value_type& elem){ std::cout << elem.first << " " << elem.second << "\n"; });
}