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#include <algorithm>
#include <fstream>
#include <iostream>
#include <iterator>
#include <limits>
#include <map>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
struct Entry {
Entry(long destination, long source, long amount) // NOLINT
: destination_(destination)
, source_(source)
, amount_(amount)
{
}
[[nodiscard]] bool in_range(long value) const
{
return source_ <= value && value < (source_ + amount_);
}
[[nodiscard]] long get_destination(long value) const
{
auto delta = value - source_;
return destination_ + delta;
}
long destination_;
long source_;
long amount_;
};
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;
}
void
part1()
{
auto lines = read_file("data/day05.txt");
auto read_ints = [](const string& line) {
stringstream iss{ line };
return vector<long>{ istream_iterator<long>{ iss }, istream_iterator<long>{} };
};
auto seeds = read_ints(lines[0].substr(6));
map<string, string> category_mapping{};
map<string, vector<Entry>> range_mapping{};
// read blocks
for ( size_t idx = 1; idx < lines.size(); ) {
++idx; // skip empty line
auto description = lines[idx++];
description.erase(description.find(' '));
auto parts = split(description, '-');
category_mapping[parts[0]] = parts[2];
vector<Entry> mapping{};
for ( ; idx < lines.size() && !lines[idx].empty(); ++idx ) {
auto values = read_ints(lines[idx]);
auto destination = values[0];
auto source = values[1];
auto amount = values[2];
mapping.emplace_back(destination, source, amount);
}
range_mapping[parts[0]] = mapping;
}
auto min_value = numeric_limits<long>::max();
for ( auto seed: seeds ) {
for ( string category{ "seed" }; !category.empty(); category = category_mapping[category] ) {
const auto& ranges = range_mapping[category];
for (const auto& range: ranges) {
if (range.in_range(seed)) {
seed = range.get_destination(seed);
break;
}
}
}
min_value = min(min_value, seed);
}
cout << min_value << endl;
}
void
part2()
{
auto lines = read_file("data/day05-sample1.txt");
auto read_ints = [](const string& line) {
stringstream iss{ line };
return vector<long>{ istream_iterator<long>{ iss }, istream_iterator<long>{} };
};
auto seeds = read_ints(lines[0].substr(6));
map<string, string> category_mapping{};
map<string, vector<Entry>> range_mapping{};
// read blocks
for ( size_t idx = 1; idx < lines.size(); ) {
++idx; // skip empty line
auto description = lines[idx++];
description.erase(description.find(' '));
auto parts = split(description, '-');
category_mapping[parts[0]] = parts[2];
vector<Entry> mapping{};
for ( ; idx < lines.size() && !lines[idx].empty(); ++idx ) {
auto values = read_ints(lines[idx]);
auto destination = values[0];
auto source = values[1];
auto amount = values[2];
mapping.emplace_back(destination, source, amount);
}
range_mapping[parts[0]] = mapping;
}
// brute force -- slow, but works
auto min_value = numeric_limits<long>::max();
for ( size_t idx = 0; idx != seeds.size(); idx += 2 ) {
for ( auto start = seeds[idx]; start != seeds[idx] + seeds[idx+1]; ++start ) {
auto seed = start;
for ( string category{ "seed" }; !category.empty(); category = category_mapping[category] ) {
const auto& ranges = range_mapping[category];
for (const auto& range: ranges) {
if (range.in_range(seed)) {
seed = range.get_destination(seed);
break;
}
}
}
min_value = min(min_value, seed);
}
}
cout << min_value << endl;
}
int
main()
{
part1();
part2();
}
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