Initial work done on part 2, but I'm not sure I'll keep the method I'm using. I might have to refactor it out into a function so that it can be called with any particular direction so that when I'm testing potential pathways I can change directions, too.

2024/6/main.cpp

@@ -8,12 +8,6 @@
 #include <unistd.h>
 #include <vector>
 
-struct Position {
-	// NOTE(dev): Could do enum empty/reached/blocked, but I'm not interested.
-	bool blocked = false;
-	bool reached = false;
-};
-
 enum Direction {
 	UP = 0,
 	RIGHT,
@@ -21,6 +15,36 @@ enum Direction {
 	LEFT
 };
 
+struct Position {
+	// NOTE(dev): Could do enum empty/reached/blocked, but I'm not interested.
+	bool blocked = false;
+	std::map<Direction, bool> reached;
+
+	bool Reached() const {
+		return reached.size();
+	}
+	char ReachedChar() const {
+		bool up_or_down = false;
+		bool left_or_right = false;
+		if(reached.contains(Direction::UP) || reached.contains(Direction::DOWN))
+			up_or_down = true;
+		if(reached.contains(Direction::LEFT) || reached.contains(Direction::RIGHT))
+			left_or_right = true;
+
+		if(up_or_down != left_or_right)
+		{
+			if(up_or_down)
+				return '|';
+			else
+				return '-';
+		}
+		else if(up_or_down)
+			return '+';
+		else
+			return ' ';
+	};
+};
+
 struct Player {
 	std::pair<int, int> location;
 	Direction direction = Direction::UP;
@@ -28,7 +52,7 @@ struct Player {
 
 int main()
 {
-	const std::string filename = "data.txt";
+	const std::string filename = "data_test.txt";
 	std::ifstream ifs(filename);
 	if(!ifs.is_open())
 	{
@@ -75,8 +99,8 @@ int main()
 				else
 				{
 					const auto &pos = level[{x, y}];
-					if(pos.reached)
-						std::cout << "X";
+					if(pos.Reached())
+						std::cout << pos.ReachedChar();
 					else if(pos.blocked)
 						std::cout << "#";
 					else
@@ -85,6 +109,9 @@ int main()
 			}
 			std::cout << std::endl;
 		}
+
+		std::cout << std::endl;
+		std::cout << "PT2 Total: " << total_pt2 << std::endl;
 	};
 
 	// Parse Input
@@ -101,7 +128,7 @@ int main()
 				pos.blocked = true;
 			if(value == '^') // always up?
 			{
-				pos.reached = true;
+				pos.reached[Direction::UP] = true;
 				player.location = {x, y};
 			}
 
@@ -123,8 +150,6 @@ int main()
 
 	std::cout << std::endl;
 
-	// while(player.location.first >= 0 && player.location.first < max_x &&
-	//       player.location.second >= 0 && player.location.second < max_y)
 	while(true)
 	{
 		std::pair<int, int> next_location = player.location;
@@ -150,13 +175,90 @@ int main()
 			break;
 		}
 		if(level[next_location].blocked)
+		{
+			// NOTE(dev): Also check if the next potential position is the last space before a turn,
+			//             as then the up/down or left/right flag wouldn't be set, but the
+			//             left/right or up/down flag would be.
+			level[player.location].reached[player.direction] = true;
 			player.direction = static_cast<Direction>(((int(player.direction)) + 1) % 4);
+			level[player.location].reached[player.direction] = true;
+		}
 		else
 		{
-			level[next_location].reached = true;
+			// TODO(dev): Need to handle the scenario where you've yet to explore a section but it
+			//             would result in a loop.
+			//      e.g.: Placing a stopping point at the O
+			//
+			//    #     #
+			//    +->O  #
+			//   #|     #
+			//    S #   #
+			// #        #
+			//     #    #
+			//
+			//      IDEA: Follow turns when exploring a direction like that.  Snake your way until
+			//             you fall off the map or you line up with a square you've been in before
+			std::map<Direction, bool> could_loop;
+			// Part 2: If you could loop in this next position, COUNT IT
+			if(player.direction == Direction::DOWN)
+			{
+				// search left of new position to see if you've been in this horizontal bit:
+				for(int x = next_location.first; x >= 0; --x)
+				{
+					std::pair<int,int> potential_position = { x, next_location.second };
+					if(level[potential_position].reached.contains(Direction::LEFT))
+					{
+						could_loop[Direction::LEFT] = true;
+						break;
+					}
+				}
+			}
+			else if(player.direction == Direction::UP)
+			{
+				// search right of new position to see if you've been in this horizontal bit:
+				for(int x = next_location.first; x < max_x; ++x)
+				{
+					std::pair<int,int> potential_position = { x, next_location.second };
+					if(level[potential_position].reached.contains(Direction::RIGHT))
+					{
+						could_loop[Direction::RIGHT] = true;
+						break;
+					}
+				}
+			}
+			else if(player.direction == Direction::LEFT)
+			{
+				// search left of new position to see if you've been in this horizontal bit:
+				for(int y = next_location.second; y >= 0; --y)
+				{
+					std::pair<int,int> potential_position = { next_location.first, y };
+					if(level[potential_position].reached.contains(Direction::UP))
+					{
+						could_loop[Direction::UP] = true;
+						break;
+					}
+				}
+			}
+			else
+			{
+				// search left of new position to see if you've been in this horizontal bit:
+				for(int y = next_location.second; y < max_y; ++y)
+				{
+					std::pair<int,int> potential_position = { next_location.first, y };
+					if(level[potential_position].reached.contains(Direction::DOWN))
+					{
+						could_loop[Direction::DOWN] = true;
+						break;
+					}
+				}
+			}
+			total_pt2 += could_loop.size();
+
+			level[next_location].reached[player.direction] = true;
 			player.location = next_location;
-			// DebugPrint();
-			// usleep(20000);
+
+			DebugPrint();
+			usleep(500000);
 		}
 	}
 
@@ -164,7 +266,7 @@ int main()
 
 	for(auto y = 0; y < max_y; ++y)
 		for(auto x = 0; x < max_x; ++x)
-			if(level[{x,y}].reached)
+			if(level[{x,y}].Reached())
 				++total;
 
 	std::cout << std::endl;