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#include <fstream>
#include <iostream>
#include <map>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
using puzzle_t = vector<pair<long, long>>;
puzzle_t
read_file_part1(string_view filename, long& border_steps)
{
static map<char, pair<int, int>> movement = {
{ 'U', { 0, -1 } }, // up
{ 'D', { 0, 1 } }, // down
{ 'L', { -1, 0 } }, // left
{ 'R', { 1, 0 } }, // right
};
border_steps = 0;
fstream input{ filename };
puzzle_t data;
data.emplace_back(0, 0);
for ( string line; getline(input, line); ) {
char dir{};
long steps{};
stringstream sstrm{ line };
if ( sstrm >> dir >> steps ) {
data.emplace_back(get<0>(data.back()) + get<0>(movement[dir]) * steps,
get<1>(data.back()) + get<1>(movement[dir]) * steps);
border_steps += steps;
}
}
return data;
}
puzzle_t
read_file_part2(string_view filename, long& border_steps)
{
static map<char, pair<int, int>> movement = {
{ '0', { 1, 0 } }, // right
{ '1', { 0, 1 } }, // down
{ '2', { -1, 0 } }, // left
{ '3', { 0, -1 } }, // up
};
border_steps = 0;
fstream input{ filename };
puzzle_t data;
data.emplace_back(0, 0);
for ( string line; getline(input, line); ) {
char dir{};
long steps{};
string hexcode;
stringstream sstrm{ line };
if ( sstrm >> dir >> steps >> hexcode ) {
steps = stol(hexcode.substr(2, 5), nullptr, 16);
dir = hexcode[7];
data.emplace_back(get<0>(data.back()) + get<0>(movement[dir]) * steps,
get<1>(data.back()) + get<1>(movement[dir]) * steps);
border_steps += steps;
}
}
return data;
}
long
shoelace(const puzzle_t& puzzle, const long border_steps)
{
long area = 0;
for ( size_t i = 1; i < puzzle.size(); ++i ) {
const auto [x1, y1] = puzzle[i - 1];
const auto [x2, y2] = puzzle[i];
area += (x1 * y2 - y1 * x2);
}
return (border_steps + area) / 2 + 1;
}
void
part1()
{
long border_steps = 0;
auto puzzle = read_file_part1("data/day18.txt", border_steps);
cout << shoelace(puzzle, border_steps) << endl;
}
void
part2()
{
long border_steps = 0;
auto puzzle = read_file_part2("data/day18.txt", border_steps);
cout << shoelace(puzzle, border_steps) << endl;
}
int
main()
{
part1();
part2();
}
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