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#include <fstream>
#include <iostream>
#include <map>
#include <regex>
#include <set>
#include <sstream>
#include <string>
#include <tuple>
#include <vector>
using namespace std;
vector<string>
split(const string& line, const regex& sep)
{
return { sregex_token_iterator(line.begin(), line.end(), sep, -1), {} };
}
vector<tuple<vector<string>, long, string>>
read_file(const string& filename)
{
fstream input{ filename };
vector<tuple<vector<string>, long, string>> result;
for ( string line; getline(input, line); ) {
static const regex sep{ "[\\[\\]-]" };
auto parts = split(line, sep);
auto checksum = parts.at(parts.size() - 1);
parts.pop_back();
auto selector = stol(parts.at(parts.size() - 1));
parts.pop_back();
result.emplace_back(parts, selector, checksum);
}
return result;
}
void
part1(const vector<tuple<vector<string>, long, string>>& data)
{
long sum = 0;
for ( const auto& [ids, selector, checksum]: data ) {
map<char, long> counts;
for ( const auto& id: ids ) {
for ( const auto chr: id ) {
++counts[chr];
}
}
set<tuple<long, char>> tops;
for ( const auto& [chr, count]: counts ) {
tops.emplace(-count, chr);
}
string result;
for ( const auto& [count, chr]: tops ) {
result += chr;
}
if ( result.starts_with(checksum) ) {
sum += selector;
}
}
cout << sum << endl;
}
void
part2(const vector<tuple<vector<string>, long, string>>& lines)
{
auto rot = [](string str, int n) {
for ( auto& chr: str ) {
chr = ((chr - 'a' + n) % 26) + 'a';
}
return str;
};
auto is_northpole = [&](const string& str, int n) {
return rot(str, n) == "northpole";
};
for ( const auto& line: lines ) {
const auto& ids = get<0>(line);
const auto selector = get<1>(line);
if ( ranges::any_of(ids, [&](auto& str) { return is_northpole(str, (int) selector); }) ) {
cout << selector << endl;
return;
}
}
}
int
main()
{
auto data = read_file("data/day04.txt");
part1(data);
part2(data);
}
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