97 lines
2.0 KiB
C++
97 lines
2.0 KiB
C++
//
|
|
// Created by Matthew Gretton-Dann on 09/12/2022.
|
|
//
|
|
|
|
#include <iostream>
|
|
#include <numeric>
|
|
#include <set>
|
|
#include <string>
|
|
#include <utility>
|
|
|
|
using Int = std::int64_t;
|
|
using Pos = std::pair<Int, Int>;
|
|
|
|
struct compare_pos
|
|
{
|
|
constexpr auto operator()(Pos const& l, Pos const& r) const noexcept
|
|
{
|
|
if (l.second < r.second) {
|
|
return true;
|
|
}
|
|
if (l.second == r.second && l.first < r.first) {
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
};
|
|
|
|
struct State
|
|
{
|
|
State() { visited_.insert(tail_pos_);
|
|
}
|
|
|
|
auto move(Pos dir, Int steps)
|
|
{
|
|
for (Int i{0}; i != steps; ++i) {
|
|
head_pos_.first += dir.first;
|
|
head_pos_.second += dir.second;
|
|
|
|
if (std::abs(head_pos_.first - tail_pos_.first) > 1 ||
|
|
std::abs(head_pos_.second - tail_pos_.second) > 1) {
|
|
if (tail_pos_.first < head_pos_.first) {
|
|
++tail_pos_.first;
|
|
}
|
|
if (tail_pos_.first > head_pos_.first) {
|
|
--tail_pos_.first;
|
|
}
|
|
if (tail_pos_.second < head_pos_.second) {
|
|
++tail_pos_.second;
|
|
}
|
|
if (tail_pos_.second > head_pos_.second) {
|
|
--tail_pos_.second;
|
|
}
|
|
visited_.insert(tail_pos_);
|
|
}
|
|
}
|
|
}
|
|
|
|
[[nodiscard]] auto visited_count() const noexcept { return visited_.size(); }
|
|
|
|
Pos head_pos_{0, 0};
|
|
Pos tail_pos_{0, 0};
|
|
std::set<Pos, compare_pos> visited_;
|
|
};
|
|
|
|
auto main() -> int
|
|
{
|
|
std::string line;
|
|
State state;
|
|
|
|
while (std::getline(std::cin, line) && !line.empty()) {
|
|
auto item{line[0]};
|
|
Pos dir{0, 0};
|
|
Int const amount{std::stoll(line.substr(2))};
|
|
switch (item) {
|
|
case 'L':
|
|
dir.first = -1;
|
|
break;
|
|
case 'R':
|
|
dir.first = 1;
|
|
break;
|
|
case 'U':
|
|
dir.second = 1;
|
|
break;
|
|
case 'D':
|
|
dir.second = -1;
|
|
break;
|
|
default:
|
|
std::cerr << "Unable to interpret: " << line << '\n';
|
|
return EXIT_FAILURE;
|
|
}
|
|
state.move(dir, amount);
|
|
}
|
|
|
|
std::cout << "Number of locations visited: " << state.visited_count() << '\n';
|
|
return 0;
|
|
}
|