2023 Day 10
This commit is contained in:
135
2023/puzzle-10-01.cc
Normal file
135
2023/puzzle-10-01.cc
Normal file
@@ -0,0 +1,135 @@
|
||||
#include <cassert>
|
||||
#include <cstdint>
|
||||
#include <cstdlib>
|
||||
#include <iostream>
|
||||
#include <string>
|
||||
#include <utility>
|
||||
#include <vector>
|
||||
|
||||
using Int = std::int64_t;
|
||||
using NumVec = std::vector<Int>;
|
||||
using Pos = std::pair<std::size_t, std::size_t>; // (x, y) pair
|
||||
|
||||
[[nodiscard]] constexpr auto operator==(Pos const& lhs, Pos const& rhs) -> bool
|
||||
{
|
||||
return lhs.first == rhs.first && lhs.second == rhs.second;
|
||||
}
|
||||
|
||||
struct Grid
|
||||
{
|
||||
void push_line(std::string const& line)
|
||||
{
|
||||
if (auto x{line.find('S')}; x != std::string::npos) {
|
||||
assert(animal_.first == std::string::npos);
|
||||
animal_.first = x;
|
||||
animal_.second = grid_.size();
|
||||
}
|
||||
grid_.push_back(line);
|
||||
}
|
||||
|
||||
[[nodiscard]] auto animal_pos() const -> Pos { return animal_; }
|
||||
|
||||
[[nodiscard]] auto width() const -> std::size_t { return grid_.front().size(); }
|
||||
[[nodiscard]] auto height() const -> std::size_t { return grid_.size(); }
|
||||
|
||||
[[nodiscard]] auto walk_pipes(Pos const& start, Pos pos) const -> std::pair<Pos, std::size_t>
|
||||
{
|
||||
auto last{start};
|
||||
std::size_t steps{0};
|
||||
while (true) {
|
||||
auto const [x, y] = pos;
|
||||
auto const c{grid_[y][x]};
|
||||
if (c == '.' || c == 'S') { break; }
|
||||
if (start == pos) { break; }
|
||||
|
||||
if (c == '|' || c == 'L' || c == 'J') {
|
||||
if (Pos const next_pos{x, y - 1}; y > 0 && next_pos != last) {
|
||||
last = pos;
|
||||
pos = next_pos;
|
||||
++steps;
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
if (c == '|' || c == 'F' || c == '7') {
|
||||
if (Pos const next_pos{x, y + 1}; y < height() - 1 && next_pos != last) {
|
||||
last = pos;
|
||||
pos = next_pos;
|
||||
++steps;
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
if (c == '-' || c == '7' || c == 'J') {
|
||||
if (Pos const next_pos{x - 1, y}; x > 0 && next_pos != last) {
|
||||
last = pos;
|
||||
pos = next_pos;
|
||||
++steps;
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
if (c == '-' || c == 'L' || c == 'F') {
|
||||
if (Pos const next_pos{x + 1, y}; x < width() - 1 && next_pos != last) {
|
||||
last = pos;
|
||||
pos = next_pos;
|
||||
++steps;
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
std::abort();
|
||||
}
|
||||
|
||||
return std::make_pair(pos, steps);
|
||||
}
|
||||
|
||||
private:
|
||||
std::vector<std::string> grid_;
|
||||
Pos animal_{std::string::npos, std::string::npos};
|
||||
};
|
||||
|
||||
auto main() -> int try {
|
||||
std::string line;
|
||||
Grid grid;
|
||||
|
||||
while (std::getline(std::cin, line)) {
|
||||
grid.push_line(line);
|
||||
}
|
||||
|
||||
auto animal = grid.animal_pos();
|
||||
|
||||
if (animal.second > 0) {
|
||||
auto [end_pos, length] = grid.walk_pipes(animal, {animal.first, animal.second - 1});
|
||||
if (end_pos == animal) {
|
||||
std::cout << "Started going north ended back at animal: " << length / 2 + 1 << '\n';
|
||||
}
|
||||
}
|
||||
|
||||
if (animal.first > 0) {
|
||||
auto [end_pos, length] = grid.walk_pipes(animal, {animal.first - 1, animal.second});
|
||||
if (end_pos == animal) {
|
||||
std::cout << "Started going west ended back at animal: " << length / 2 + 1 << '\n';
|
||||
}
|
||||
}
|
||||
|
||||
if (animal.second < grid.height() - 1) {
|
||||
auto [end_pos, length] = grid.walk_pipes(animal, {animal.first, animal.second + 1});
|
||||
if (end_pos == animal) {
|
||||
std::cout << "Started going south ended back at animal: " << length / 2 + 1 << '\n';
|
||||
}
|
||||
}
|
||||
|
||||
if (animal.first < grid.width() - 1) {
|
||||
auto [end_pos, length] = grid.walk_pipes(animal, {animal.first + 1, animal.second});
|
||||
if (end_pos == animal) {
|
||||
std::cout << "Started going east ended back at animal: " << length / 2 + 1 << '\n';
|
||||
}
|
||||
}
|
||||
|
||||
return EXIT_SUCCESS;
|
||||
}
|
||||
catch (...) {
|
||||
std::cerr << "Uncaught exception.\n";
|
||||
return EXIT_FAILURE;
|
||||
}
|
||||
374
2023/puzzle-10-02.cc
Normal file
374
2023/puzzle-10-02.cc
Normal file
@@ -0,0 +1,374 @@
|
||||
#include <algorithm>
|
||||
#include <cassert>
|
||||
#include <cstdint>
|
||||
#include <cstdlib>
|
||||
#include <iostream>
|
||||
#include <string>
|
||||
#include <utility>
|
||||
#include <vector>
|
||||
|
||||
using Int = std::int64_t;
|
||||
using NumVec = std::vector<Int>;
|
||||
using Pos = std::pair<std::size_t, std::size_t>; // (x, y) pair
|
||||
|
||||
[[nodiscard]] constexpr auto operator==(Pos const& lhs, Pos const& rhs) -> bool
|
||||
{
|
||||
return lhs.first == rhs.first && lhs.second == rhs.second;
|
||||
}
|
||||
|
||||
struct Grid;
|
||||
auto operator<<(std::ostream& os, Grid const& grid) -> std::ostream&;
|
||||
|
||||
struct Grid
|
||||
{
|
||||
void push_line(std::string const& line)
|
||||
{
|
||||
if (auto x{line.find('S')}; x != std::string::npos) {
|
||||
assert(animal_.first == std::string::npos);
|
||||
animal_.first = x;
|
||||
animal_.second = grid_.size();
|
||||
}
|
||||
grid_.push_back(line);
|
||||
}
|
||||
|
||||
[[nodiscard]] auto animal_pos() const -> Pos { return animal_; }
|
||||
|
||||
[[nodiscard]] auto width() const -> std::size_t { return grid_.front().size(); }
|
||||
[[nodiscard]] auto height() const -> std::size_t { return grid_.size(); }
|
||||
|
||||
[[nodiscard]] auto at(Pos const& pos) const -> char { return grid_[pos.second][pos.first]; }
|
||||
void set(Pos const& pos, char c) { grid_[pos.second][pos.first] = c; }
|
||||
|
||||
[[nodiscard]] auto walk_pipes(Pos const& start, Pos pos) const -> std::pair<Pos, std::size_t>
|
||||
{
|
||||
auto last{start};
|
||||
std::size_t steps{0};
|
||||
while (true) {
|
||||
auto const [x, y] = pos;
|
||||
auto const c{grid_[y][x]};
|
||||
if (c == '.' || c == 'S') { break; }
|
||||
if (start == pos) { break; }
|
||||
|
||||
if (c == '|' || c == 'L' || c == 'J') {
|
||||
if (Pos const next_pos{x, y - 1}; y > 0 && next_pos != last) {
|
||||
last = pos;
|
||||
pos = next_pos;
|
||||
++steps;
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
if (c == '|' || c == 'F' || c == '7') {
|
||||
if (Pos const next_pos{x, y + 1}; y < height() - 1 && next_pos != last) {
|
||||
last = pos;
|
||||
pos = next_pos;
|
||||
++steps;
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
if (c == '-' || c == '7' || c == 'J') {
|
||||
if (Pos const next_pos{x - 1, y}; x > 0 && next_pos != last) {
|
||||
last = pos;
|
||||
pos = next_pos;
|
||||
++steps;
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
if (c == '-' || c == 'L' || c == 'F') {
|
||||
if (Pos const next_pos{x + 1, y}; x < width() - 1 && next_pos != last) {
|
||||
last = pos;
|
||||
pos = next_pos;
|
||||
++steps;
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
std::abort();
|
||||
}
|
||||
|
||||
return std::make_pair(pos, steps);
|
||||
}
|
||||
|
||||
void hightlight_pipes(Pos const& start)
|
||||
{
|
||||
auto last{start};
|
||||
auto pos{start};
|
||||
|
||||
auto const c{at(start)};
|
||||
if (c == '|' || c == 'L' || c == 'J') { pos.second -= 1; }
|
||||
else if (c == 'F' || c == '7') { pos.second += 1; }
|
||||
else if (c == '-') { pos.first += 1; }
|
||||
else { std::abort(); }
|
||||
set(start, c == '|' ? 'v' : '>');
|
||||
|
||||
while (start != pos) {
|
||||
auto const [x, y] = pos;
|
||||
auto const c{grid_[y][x]};
|
||||
if (c == '.') { std::abort(); }
|
||||
grid_[y][x] = c == '|' ? 'v' : '>';
|
||||
|
||||
if (c == '|' || c == 'L' || c == 'J') {
|
||||
if (Pos const next_pos{x, y - 1}; y > 0 && next_pos != last) {
|
||||
last = pos;
|
||||
pos = next_pos;
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
if (c == '|' || c == 'F' || c == '7') {
|
||||
if (Pos const next_pos{x, y + 1}; y < height() - 1 && next_pos != last) {
|
||||
last = pos;
|
||||
pos = next_pos;
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
if (c == '-' || c == '7' || c == 'J') {
|
||||
if (Pos const next_pos{x - 1, y}; x > 0 && next_pos != last) {
|
||||
last = pos;
|
||||
pos = next_pos;
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
if (c == '-' || c == 'L' || c == 'F') {
|
||||
if (Pos const next_pos{x + 1, y}; x < width() - 1 && next_pos != last) {
|
||||
last = pos;
|
||||
pos = next_pos;
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
std::abort();
|
||||
}
|
||||
}
|
||||
|
||||
auto flood_fill()
|
||||
{
|
||||
/* Ensure every character is either an edge, or a '.' for outside, maybe inside, and a '*'
|
||||
* for the initial starting locations.
|
||||
*/
|
||||
for (auto& row : grid_) {
|
||||
/* We know we're inside if we've passed an odd number of vertical walls and no corners/
|
||||
* horizontal walls.
|
||||
*/
|
||||
bool inside = false;
|
||||
bool definite = true;
|
||||
for (auto& c : row) {
|
||||
if (c == 'v') { inside = !inside; }
|
||||
else if (c == '>') { definite = false; }
|
||||
else if (inside && definite) {
|
||||
c = '*';
|
||||
}
|
||||
else { c = '.'; }
|
||||
}
|
||||
}
|
||||
|
||||
/* Very simple algorithm, that just iterates over all squares until we don't change anything */
|
||||
bool again{true};
|
||||
while (again) {
|
||||
again = false;
|
||||
for (std::size_t y{0}; y != height(); ++y) {
|
||||
for (std::size_t x{0}; x != width(); ++x) {
|
||||
if (grid_[y][x] != '.') { continue; }
|
||||
if ((y > 0 && grid_[y - 1][x] == '*') || (x > 0 && grid_[y][x - 1] == '*') || (
|
||||
y < height() - 1 && grid_[y + 1][x] == '*') || (
|
||||
x < width() - 1 && grid_[y][x + 1] == '*')) {
|
||||
grid_[y][x] = '*';
|
||||
again = true;
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/* Shrink the grid by a factor of two in all directions. We take the even places to be the new
|
||||
* entry in the new grid.
|
||||
*
|
||||
* So grid.enlarge().shrink() should produce the same grid as grid.
|
||||
*/
|
||||
[[nodiscard]] auto shrink() const -> Grid
|
||||
{
|
||||
Grid new_grid;
|
||||
for (std::size_t y{0}; y < height(); y += 2) {
|
||||
std::string line;
|
||||
for (std::size_t x{0}; x < width(); x += 2) {
|
||||
line += grid_[y][x];
|
||||
}
|
||||
new_grid.push_line(line);
|
||||
}
|
||||
return new_grid;
|
||||
}
|
||||
|
||||
/* Enlarge the grid by a factor of two in each direction.
|
||||
*
|
||||
* The contents of grid_[y][x] are mapped to grid_[y * 2][x * 2] and the appropriate additional
|
||||
* characters are added.
|
||||
*/
|
||||
[[nodiscard]] auto enlarge() const -> Grid
|
||||
{
|
||||
Grid new_grid;
|
||||
for (auto const& row : grid_) {
|
||||
std::string line1;
|
||||
std::string line2;
|
||||
for (auto const c : row) {
|
||||
if (c == '.') {
|
||||
line1 += "..";
|
||||
line2 += "..";
|
||||
}
|
||||
if (c == '-') {
|
||||
line1 += "--";
|
||||
line2 += "..";
|
||||
}
|
||||
if (c == '7') {
|
||||
line1 += "7.";
|
||||
line2 += "|.";
|
||||
}
|
||||
if (c == 'F') {
|
||||
line1 += "F-";
|
||||
line2 += "|.";
|
||||
}
|
||||
if (c == '|') {
|
||||
line1 += "|.";
|
||||
line2 += "|.";
|
||||
}
|
||||
if (c == 'J') {
|
||||
line1 += "J.";
|
||||
line2 += "..";
|
||||
}
|
||||
if (c == 'L') {
|
||||
line1 += "L-";
|
||||
line2 += "..";
|
||||
}
|
||||
}
|
||||
new_grid.push_line(line1);
|
||||
new_grid.push_line(line2);
|
||||
}
|
||||
|
||||
return new_grid;
|
||||
}
|
||||
|
||||
[[nodiscard]] auto count_interior() const -> std::size_t
|
||||
{
|
||||
std::size_t interior{0};
|
||||
for (auto const& row : grid_) {
|
||||
interior += std::ranges::count_if(row, [](char const c) { return c == '*'; });
|
||||
}
|
||||
|
||||
return interior;
|
||||
}
|
||||
|
||||
friend auto operator<<(std::ostream& os, Grid const& grid) -> std::ostream&;
|
||||
|
||||
private:
|
||||
std::vector<std::string> grid_;
|
||||
Pos animal_{std::string::npos, std::string::npos};
|
||||
};
|
||||
|
||||
auto operator<<(std::ostream& os, Grid const& grid) -> std::ostream&
|
||||
{
|
||||
for (auto const& row : grid.grid_) {
|
||||
os << row << '\n';
|
||||
}
|
||||
return os;
|
||||
}
|
||||
|
||||
auto main() -> int try {
|
||||
std::string line;
|
||||
Grid grid;
|
||||
|
||||
while (std::getline(std::cin, line)) {
|
||||
grid.push_line(line);
|
||||
}
|
||||
|
||||
auto animal = grid.animal_pos();
|
||||
|
||||
/* Find the loop in both directions as this tells us what the animal pipe piece should be. */
|
||||
bool east{false};
|
||||
bool south{false};
|
||||
bool west{false};
|
||||
bool north{false};
|
||||
if (animal.second > 0) {
|
||||
Pos const next_pos{animal.first, animal.second - 1};
|
||||
if (auto const c{grid.at(next_pos)}; c == '|' || c == 'F' || c == '7') {
|
||||
auto [end_pos, length] = grid.walk_pipes(animal, next_pos);
|
||||
if (end_pos == animal) {
|
||||
std::cout << "Started going north ended back at animal: " << length / 2 + 1 << '\n';
|
||||
north = true;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
if (animal.first > 0) {
|
||||
Pos const next_pos{animal.first - 1, animal.second};
|
||||
if (auto const c{grid.at(next_pos)}; c == '-' || c == 'F' || c == 'L') {
|
||||
auto [end_pos, length] = grid.walk_pipes(animal, next_pos);
|
||||
if (end_pos == animal) {
|
||||
std::cout << "Started going west ended back at animal: " << length / 2 + 1 << '\n';
|
||||
west = true;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
if (animal.second < grid.height() - 1) {
|
||||
Pos const next_pos{animal.first, animal.second + 1};
|
||||
if (auto const c{grid.at(next_pos)}; c == '|' || c == 'J' || c == 'L') {
|
||||
auto [end_pos, length] = grid.walk_pipes(animal, next_pos);
|
||||
if (end_pos == animal) {
|
||||
std::cout << "Started going south ended back at animal: " << length / 2 + 1 << '\n';
|
||||
south = true;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
if (animal.first < grid.width() - 1) {
|
||||
Pos const next_pos{animal.first + 1, animal.second};
|
||||
if (auto const c{grid.at(next_pos)}; c == '-' || c == 'J' || c == '7') {
|
||||
auto [end_pos, length] = grid.walk_pipes(animal, next_pos);
|
||||
if (end_pos == animal) {
|
||||
std::cout << "Started going east ended back at animal: " << length / 2 + 1 << '\n';
|
||||
east = true;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/* Replace animal with pipe piece. */
|
||||
if (north && south) { grid.set(animal, '|'); }
|
||||
else if (east && west) { grid.set(animal, '-'); }
|
||||
else if (north && east) { grid.set(animal, 'L'); }
|
||||
else if (north && west) { grid.set(animal, 'J'); }
|
||||
else if (south && east) { grid.set(animal, 'F'); }
|
||||
else if (south && west) { grid.set(animal, '7'); }
|
||||
else {
|
||||
std::abort();
|
||||
}
|
||||
|
||||
/* To ensure that the interior is stongly connected we double the size of the grid in both
|
||||
* directions. This makes sure that there is always a . between two pipe edges.
|
||||
*
|
||||
* This then means we can do a very simple flood fill to find the interior.
|
||||
*
|
||||
* We then shrink the grid again and to get the interior count we want.
|
||||
*/
|
||||
auto big_grid{grid.enlarge()};
|
||||
// Mark the pipes we want to work with using > & v characters
|
||||
big_grid.hightlight_pipes(Pos{animal.first * 2, animal.second * 2});
|
||||
std::cout << "Before flood fill:\n" << big_grid;
|
||||
// Flood fill the interior with * characters
|
||||
big_grid.flood_fill();
|
||||
std::cout << "After flood fill:\n" << big_grid;
|
||||
// Shrink
|
||||
auto const small_grid = big_grid.shrink();
|
||||
// Count the number of * in the interior.
|
||||
auto const interior_count = small_grid.count_interior();
|
||||
std::cout << "Reconstituted grid\n" << small_grid;
|
||||
std::cout << "Interior count: " << interior_count << "\n";
|
||||
|
||||
return EXIT_SUCCESS;;
|
||||
}
|
||||
catch (...) {
|
||||
std::cerr << "Uncaught exception.\n";
|
||||
return EXIT_FAILURE;
|
||||
}
|
||||
Reference in New Issue
Block a user