two sum

2sum.cpp

#include <fstream>
#include <iostream>
#include <unordered_set>
#include <thread>
#include <future>

int foo(long long a, long long b, const std::unordered_set<long long>& set)
{
	int result(0);

	for (auto i = a; i < b; ++i)
	{
		for (auto&& n : set)
		{
			if (set.find(i - n) != set.end())
			{
				result++;
				break;
			}
		}
	}
	std::cout << result << std::endl;
	return result;
}

int main()
{
	auto thread_cnt = std::thread::hardware_concurrency();
	std::ifstream input_file("D:\\Playground\\2sum.txt");
	long long t;
	std::unordered_set<long long> set;
	while (input_file >> t)
	{
		set.insert(t);
	}
	auto m = -10000, n = 10000;
	std::vector<std::future<int>> fut;
	int d = (n - m) / thread_cnt;
	for (auto i = 0; i < thread_cnt; i++)
	{
		fut.push_back(std::async(foo, m, m + d, set));
		std::cout << m << " " << m + d << std::endl;
		m += d;
	}
	int r = 0;
	for (auto&& f:fut)
	{
		r += f.get();
	}

	for (auto&& x : set)
	{
		if (set.find(n - x) != set.end())
		{
			r++;
			break;
		}
	}
	return r;
}