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#include <fstream>
#include <iostream>
#include <map>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
vector<string>
read_file(string_view filename)
{
fstream input{ filename };
vector<string> data;
for ( string line; getline(input, line); ) {
data.emplace_back(line);
}
return data;
}
vector<string>
split(const string& line, char sep)
{
vector<string> parts{};
stringstream input{ line };
for ( string part; getline(input, part, sep); ) {
parts.emplace_back(part);
}
return parts;
}
template<typename T = long>
vector<T>
read_ints(const string& line)
{
vector<T> parts{};
stringstream input{ line };
for ( string part; getline(input, part, ','); ) {
parts.emplace_back(stol(part));
}
return parts;
}
vector<long>
count_groups(string_view str)
{
vector<long> groups;
size_t idx = 0U;
while ( idx != str.length() ) {
while ( idx != str.length() && str[idx] == '.' ) {
++idx;
}
if ( idx != str.length() && str[idx] == '#' ) {
auto num = 0L;
while ( idx != str.length() && str[idx] == '#' ) {
++num;
++idx;
}
groups.emplace_back(num);
}
}
return groups;
}
long
brute_force(string_view springs, const vector<long>& groups)
{
long counts = count_if(springs.begin(), springs.end(), [](char chr) { return chr == '?'; });
string test_pattern;
auto arrangements = 0L;
for ( size_t counter = 0; counter != (1U << size_t(counts)); ++counter ) {
auto bit_pattern = counter;
for ( char chr: springs ) {
if ( chr == '?' ) {
if ( (bit_pattern & 1U) != 0U ) {
test_pattern += '.';
}
else {
test_pattern += '#';
}
bit_pattern >>= 1U;
}
else {
test_pattern += chr;
}
}
if ( groups == count_groups(test_pattern) ) {
arrangements++;
}
test_pattern.clear();
}
return arrangements;
}
long
count(const string& springs, const vector<long>& groups)
{
map<tuple<string, vector<long>>, long> cache;
function<long(string, const vector<long>&)> count_rec = [&](string springs, const vector<long>& groups) -> long {
auto cached_value = cache.find(make_tuple(springs, groups));
if ( cached_value != cache.end() ) {
return cached_value->second;
}
springs.erase(0, springs.find_first_not_of('.'));
if ( springs.empty() ) {
return groups.empty() ? 1 : 0;
}
if ( groups.empty() ) {
return springs.find('#') == string_view::npos ? 1 : 0;
}
if ( springs[0] == '#' ) {
auto gidx = size_t(groups[0]);
if ( springs.length() < gidx || springs.substr(0, gidx).find('.') != string_view::npos || springs[gidx] == '#' ) {
return 0;
}
return count_rec(springs.substr(gidx + 1), { groups.begin() + 1, groups.end() });
}
auto value = count_rec(string("#") + springs.substr(1), groups) + count_rec(springs.substr(1), groups);
cache[make_tuple(springs, groups)] = value;
return value;
};
return count_rec(springs + ".", groups);
}
void
part1(const vector<string>& input)
{
auto sum = 0L;
for ( const auto& line: input ) {
auto parts = split(line, ' ');
auto springs = parts[0];
auto groups = read_ints(parts[1]);
sum += brute_force(springs, groups);
// sum += count(springs, groups);
}
cout << sum << endl;
}
void
part2(const vector<string>& input)
{
auto sum = 0L;
for ( const auto& line: input ) {
auto parts = split(line, ' ');
auto springs = parts[0] + "?" + parts[0] + "?" + parts[0] + "?" + parts[0] + "?" + parts[0];
auto groups = read_ints(parts[1] + "," + parts[1] + "," + parts[1] + "," + parts[1] + "," + parts[1]);
sum += count(springs, groups);
}
cout << sum << endl;
}
int
main()
{
const auto input = read_file("data/day12.txt");
part1(input);
part2(input);
}
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