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#include <filesystem>
#include <fstream>
#include <iostream>
#include <string>
#include <vector>
using namespace std;
namespace {
vector<string>
read_file(const filesystem::path& filename)
{
ifstream file{ filename };
vector<string> lines;
for ( string line; getline(file, line); ) {
lines.emplace_back(line);
}
return lines;
}
void
part1(const vector<string>& lines)
{
auto zeros = 0;
auto pos = 50;
for ( const auto& line: lines ) {
const auto value = stoi(line.substr(1)) % 100;
pos += (line[0] == 'L') ? (100 - value) : value;
if ( pos % 100 == 0 ) {
++zeros;
}
}
cout << "Part 1: " << zeros << '\n';
}
void
part2(const vector<string>& lines)
{
auto zeros = 0;
auto pos = 50;
for ( const auto& line: lines ) {
const auto delta = (line[0] == 'L') ? 99 : 1;
for ( auto value = stoi(line.substr(1)); value > 0; --value ) {
pos += delta;
if ( pos % 100 == 0 ) {
++zeros;
}
}
}
cout << "Part 2: " << zeros << '\n';
}
void
part2_opti(const vector<string>& lines)
{
auto zeros = 0;
auto pos = 50;
auto is_zero = [&pos] {
return pos % 100 == 0;
};
for ( const auto& line: lines ) {
const auto delta = (line[0] == 'L') ? 99 : 1;
auto value = stoi(line.substr(1));
if ( !is_zero() ) {
for ( ; value > 0 && !is_zero(); --value ) {
pos += delta;
}
if ( is_zero() ) {
++zeros;
}
}
zeros += value / 100;
value %= 100;
for ( ; value > 0; --value ) {
pos += delta;
if ( is_zero() ) {
++zeros;
}
}
}
cout << "Part2 (Opti): " << zeros << '\n';
}
} // namespace
int
main()
{
auto data = read_file("data/day01.txt");
part1(data);
part2(data);
part2_opti(data);
}
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