nick.cpp

#include <iostream>
#include <ctime>

int main() {
	const auto pentagonal_function = [](double n) -> double { return (n * ((3 * n) - 1)) / 2; };
	const auto hexagonal_function = [](double n) -> double { return n * ((2 * n) - 1); };

	auto pent_index     = 0u;
	auto hex_index      = 0u;
	auto solution_count = 1u;

	std::clock_t start = std::clock();

	while(true) {
		const auto pent = pentagonal_function(pent_index);
		const auto hex  = hexagonal_function(hex_index);
		if(pent < hex)
			++pent_index;
		else if(pent > hex)
			++hex_index;
		else if(pent == hex) {
			++solution_count;
			++pent_index;
			std::cout << "solution #" << solution_count << ":\n  pent_index: " << pent_index << "\n  hex_index: " << hex_index << "\n  y: " << pent
			          << "\n  elapsed: " << ((std::clock() - start) / (double)CLOCKS_PER_SEC) << "s\n\n";
		}
	}
}