feat: day06

Author: martabal

Cargo.lock

@@ -6,6 +6,7 @@ members = [
     "crates/day03",
     "crates/day04",
     "crates/day05",
+    "crates/day06",
     "crates/helpers",
 ]
 

Cargo.toml

@@ -16,3 +16,4 @@ Ideally, the solution does not use external crates/dependencies.
 |   3   |   ✅    |   ✅    |   ✅    |   ✅    |   ✅    |   ✅    |
 |   4   |   ✅    |   ✅    |   ✅    |   ✅    |   ✅    |   ✅    |
 |   5   |   ✅    |   ✅    |   ✅    |   ✅    |   ✅    |   ✅    |
+|   6   |   ✅    |   ✅    |   ✅    |   ✅    |   ❌    |   ❌    |

README.md

@@ -0,0 +1,231 @@
+#include <fstream>
+#include <iostream>
+#include <optional>
+#include <set>
+#include <sstream>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+const char OBJECT = '#';
+
+enum class Direction { Up, Down, Left, Right };
+
+class Lab {
+public:
+  pair<size_t, size_t> pos_init;
+  vector<vector<char>> grid;
+  pair<size_t, size_t> right_bottom_position;
+
+  Lab(const string &content) {
+    grid = parseGrid(content);
+    pos_init = findInitialPosition(content);
+    right_bottom_position = {grid.size() - 1, grid[0].size() - 1};
+  }
+
+  size_t findPath() {
+    Direction direction = Direction::Up;
+    auto current_position = pos_init;
+    set<pair<size_t, size_t>> already_explored_pos;
+    already_explored_pos.insert(pos_init);
+
+    if (pos_init.second == 0 ||
+        (pos_init.second > 0 &&
+         grid[pos_init.second][pos_init.first] == OBJECT)) {
+      direction = changeDirection(direction);
+    }
+
+    bool second_try = false;
+
+    while (true) {
+      auto [is_out, pos, _] = changePosition(direction, current_position);
+      if (is_out) {
+        break;
+      }
+      if (pos.has_value()) {
+        current_position = pos.value();
+        already_explored_pos.insert(current_position);
+        if (second_try) {
+          second_try = false;
+        }
+      } else {
+        direction = changeDirection(direction);
+        if (second_try) {
+          break;
+        }
+        second_try = true;
+      }
+    }
+
+    return already_explored_pos.size();
+  }
+
+  size_t findIfStuck() {
+    vector<vector<char>> original_grid = grid;
+    size_t count = 0;
+
+    for (size_t row = 0; row < grid.size(); ++row) {
+      for (size_t col = 0; col < grid[row].size(); ++col) {
+        if (OBJECT != grid[row][col]) {
+          grid[row][col] = OBJECT;
+          Direction direction = Direction::Up;
+          auto current_position = pos_init;
+          set<tuple<pair<size_t, size_t>, pair<size_t, size_t>, string>>
+              detect_loop;
+
+          if (pos_init.second == 0 ||
+              (pos_init.second > 0 &&
+               grid[pos_init.second][pos_init.first] == OBJECT)) {
+            direction = changeDirection(direction);
+          }
+
+          bool second_try = false;
+
+          while (true) {
+            auto [is_out, pos, block] =
+                changePosition(direction, current_position);
+            if (is_out) {
+              break;
+            }
+            if (pos.has_value()) {
+              current_position = pos.value();
+              if (second_try) {
+                second_try = false;
+              }
+            } else if (block.has_value()) {
+              string str_direction = to_string(static_cast<int>(direction));
+              auto blocking =
+                  make_tuple(current_position, block.value(), str_direction);
+              direction = changeDirection(direction);
+              if (detect_loop.count(blocking)) {
+                count += 1;
+                break;
+              }
+              detect_loop.insert(blocking);
+              second_try = true;
+            }
+          }
+
+          grid[row][col] = original_grid[row][col];
+        }
+      }
+    }
+
+    return count;
+  }
+
+private:
+  static vector<vector<char>> parseGrid(const string &content) {
+    vector<vector<char>> grid;
+    stringstream ss(content);
+    string line;
+
+    while (getline(ss, line)) {
+      vector<char> row(line.begin(), line.end());
+      for (char &c : row) {
+        if (c == '^') {
+          c = '.';
+        }
+      }
+      grid.push_back(row);
+    }
+    return grid;
+  }
+
+  static pair<size_t, size_t> findInitialPosition(const string &content) {
+    stringstream ss(content);
+    string line;
+    size_t row_idx = 0;
+
+    while (getline(ss, line)) {
+      size_t col_idx = line.find('^');
+      if (col_idx != string::npos) {
+        return {row_idx, col_idx};
+      }
+      row_idx++;
+    }
+    throw runtime_error("initial position not detected");
+  }
+
+  tuple<bool, optional<pair<size_t, size_t>>, optional<pair<size_t, size_t>>>
+  changePosition(Direction direction, pair<size_t, size_t> position) {
+    auto [y, x] = position;
+
+    switch (direction) {
+    case Direction::Up:
+      if (y == 0) {
+        return {true, nullopt, nullopt};
+      }
+      if (grid[y - 1][x] != OBJECT) {
+        return {false, make_optional(make_pair(y - 1, x)), nullopt};
+      }
+      return {false, nullopt, make_optional(make_pair(y - 1, x))};
+
+    case Direction::Left:
+      if (x == 0) {
+        return {true, nullopt, nullopt};
+      }
+      if (grid[y][x - 1] != OBJECT) {
+        return {false, make_optional(make_pair(y, x - 1)), nullopt};
+      }
+      return {false, nullopt, make_optional(make_pair(y, x - 1))};
+
+    case Direction::Down:
+      if (y + 1 > right_bottom_position.first) {
+        return {true, nullopt, nullopt};
+      }
+      if (grid[y + 1][x] != OBJECT) {
+        return {false, make_optional(make_pair(y + 1, x)), nullopt};
+      }
+      return {false, nullopt, make_optional(make_pair(y + 1, x))};
+
+    case Direction::Right:
+      if (x + 1 > right_bottom_position.second) {
+        return {true, nullopt, nullopt};
+      }
+      if (grid[y][x + 1] != OBJECT) {
+        return {false, make_optional(make_pair(y, x + 1)), nullopt};
+      }
+      return {false, nullopt, make_optional(make_pair(y, x + 1))};
+    }
+
+    return {false, nullopt, nullopt};
+  }
+
+  static Direction changeDirection(Direction direction) {
+    switch (direction) {
+    case Direction::Up:
+      return Direction::Right;
+    case Direction::Right:
+      return Direction::Down;
+    case Direction::Down:
+      return Direction::Left;
+    }
+    return Direction::Up;
+  }
+};
+
+string readFile(const string &filename) {
+  ifstream file(filename);
+  if (!file.is_open()) {
+    throw runtime_error("Could not open file");
+  }
+  stringstream buffer;
+  buffer << file.rdbuf();
+  return buffer.str();
+}
+
+int main() {
+  try {
+    string message = readFile("crates/day06/input.txt");
+    Lab grid(message);
+    // --- Part One ---
+    cout << "Part One solution: " << grid.findPath() << endl;
+    // --- Part Two ---
+    cout << "Part Two solution: " << grid.findIfStuck() << endl;
+  } catch (const exception &e) {
+    cerr << e.what() << endl;
+  }
+  return 0;
+}

cpp/day06.cc

@@ -0,0 +1,10 @@
+[package]
+name = "day06"
+version = "0.1.0"
+edition = "2021"
+
+[lints]
+workspace = true
+
+[dependencies]
+helpers = { path = "../helpers"}

crates/day06/Cargo.toml

@@ -0,0 +1,10 @@
+....#.....
+.........#
+..........
+..#.......
+.......#..
+..........
+.#..^.....
+........#.
+#.........
+......#...

crates/day06/example_input.txt

@@ -0,0 +1,10 @@
+....#.....
+.........#
+..........
+..#.......
+.......#..
+..........
+.#..^.....
+........#.
+#.........
+......#...