freqs.cpp

// See http://ideone.com/VvuV4B

#include <algorithm>
#include <iostream>
#include <fstream>
#include <iterator>
#include <unordered_map>
#include <vector>

int main(int argc, char* argv[]) {
	if(argc != 3) return 1;
	std::ifstream in(argv[1]);
	std::ofstream out(argv[2]);
	if(!in || !out) return 1;
    //auto& in = std::cin;
    //auto& out = std::cout;
	
	std::unordered_map<std::string, std::size_t> freqs;
	std::string word;
	while(in)
	{
		auto c = in.get();
		if(std::isalpha(c))
		{
			word.append(1, std::tolower(c));
		}
		else if(!word.empty())
		{
			++freqs[word];
			word.clear();
		}
	}
	
	using Item = std::pair<std::string, std::size_t>;
	std::vector<Item> results;
	
	results.reserve(freqs.size());
	std::move(freqs.begin(), freqs.end(), std::back_inserter(results));
	
	std::sort(results.begin(), results.end(), [](Item& a, Item& b)
	{
		return a.second > b.second || (a.second == b.second &&
		std::lexicographical_compare(a.first.begin(), a.first.end(), b.first.begin(), b.first.end())
		);
	});

	for(auto& item : results)
	{
		out << item.second << ' ' << item.first << '\n';
	}
	return 0;
}

40 min

It looks like you need to include cctype to use std::ialpha