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#include <array>
#include <fstream>
#include <iostream>
#include <iterator>
#include <numeric>
#include <regex>
#include <vector>
using namespace std;
vector<string>
split(string_view line, string_view delimiter)
{
string::size_type pos_start = 0;
string::size_type pos_end = 0;
vector<string> res;
while ( (pos_end = line.find(delimiter, pos_start)) != string::npos ) {
res.emplace_back(line.substr(pos_start, pos_end - pos_start));
pos_start = pos_end + delimiter.length();
}
if ( pos_start != line.size() ) {
res.emplace_back(line.substr(pos_start));
}
return res;
}
vector<array<long, 6>>
read_file(string_view filename)
{
static const regex pattern{ R"((\d+).*\+(\d+).*\+(\d+).*\+(\d+).*=(\d+).*=(\d+))" };
fstream input{ filename };
string content{ istreambuf_iterator<char>{ input }, {} };
auto parts = split(content, "\n\n");
vector<array<long, 6>> data;
for ( auto part: parts ) {
part.erase(std::remove(part.begin(), part.end(), '\n'), part.cend());
smatch matches;
if ( regex_search(part, matches, pattern) ) {
data.push_back({ stoi(matches[1]),
stoi(matches[2]),
stoi(matches[3]),
stoi(matches[4]),
stoi(matches[5]),
stoi(matches[6]) });
}
}
return data;
}
long
test_brute_force(const array<long, 6>& machine)
{
const auto button_a_x = machine[0];
const auto button_a_y = machine[1];
const auto button_b_x = machine[2];
const auto button_b_y = machine[3];
const auto price_x = machine[4];
const auto price_y = machine[5];
auto min_value = numeric_limits<long>::max();
for ( long i = 0; i != 100; ++i ) {
for ( long j = 0; j != 100; ++j ) {
if ( i * button_a_x + j * button_b_x == price_x &&
i * button_a_y + j * button_b_y == price_y ) {
min_value = min(min_value, i * 3 + j);
}
}
}
return min_value != numeric_limits<long>::max() ? min_value : 0;
}
long
test_algorithmic(const array<long, 6>& machine)
{
const auto button_a_x = machine[0];
const auto button_a_y = machine[1];
const auto button_b_x = machine[2];
const auto button_b_y = machine[3];
const auto price_x = machine[4] + 10000000000000;
const auto price_y = machine[5] + 10000000000000;
const auto i = (price_x * button_b_y - price_y * button_b_x) / (button_a_x * button_b_y - button_a_y * button_b_x);
const auto j = (price_x - button_a_x * i) / button_b_x;
if ( i * button_a_x + j * button_b_x == price_x &&
i * button_a_y + j * button_b_y == price_y ) {
return i * 3 + j;
}
return 0;
}
void
part1(const vector<array<long, 6>>& machines)
{
cout << accumulate(machines.begin(), machines.end(), 0L, [](auto init, const auto& machine) {
return init + test_brute_force(machine);
}) << endl;
}
void
part2(const vector<array<long, 6>>& machines)
{
cout << accumulate(machines.begin(), machines.end(), 0L, [](auto init, const auto& machine) {
return init + test_algorithmic(machine);
}) << endl;
}
int
main()
{
auto data = read_file("data/day13.txt");
part1(data);
part2(data);
}
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