Day09

src/days/09/Day09.cpp

@@ -1,9 +1,110 @@
 #include "Day09.h"
 
 Result Day09::Task1() {
-	return Day::Task1();
+	vector<Move> moves = parseMoves();
+	set<PositionS> visited({{0, 0}});
+
+	Position head(0, 0);
+	Position tail(0, 0);
+
+	Position prevHead = head;
+
+	auto updateTail = [&head, &tail, &prevHead](){
+		if (abs(head.x - tail.x) >= 2 || abs(head.y - tail.y) >= 2){
+			tail = prevHead;
+		}
+	};
+
+	for (const Move &move : moves){
+		Direction d = move.first;
+		int amount = move.second;
+
+		for (int step = 0; step < amount; step++){
+			prevHead = head;
+			head += d;
+			updateTail();
+			visited.insert({tail.x, tail.y});
+		}
+	}
+
+	return to_string(visited.size());
 }
 
 Result Day09::Task2() {
-	return Day::Task2();
+	vector<Move> moves = parseMoves();
+	set<PositionS> visited({{0, 0}});
+
+	Position head(0, 0);
+	vector<Position*> rope(10);
+	rope[0] = &head;
+	for (int i = 1; i < rope.size(); i++) rope[i] = new Position;
+
+	auto updateTail = [rope](){
+		for (int i = 1; i < rope.size(); i++){
+			Position& current = *rope[i];
+			Position& front = *rope[i - 1];
+			int diffX = front.x - current.x;
+			int diffY = front.y - current.y;
+			if (abs(diffX) > 1 && abs(diffY) > 1){
+				current.x += diffX / abs(diffX);
+				current.y += diffY / abs(diffY);
+			}
+			else if (abs(diffX) > 1){
+				current.x += diffX / abs(diffX);
+				current.y = front.y;
+			}
+			else if (abs(diffY) > 1){
+				current.y += diffY / abs(diffY);
+				current.x = front.x;
+			}
+		}
+	};
+
+	for (const Move &move : moves){
+		Direction d = move.first;
+		int amount = move.second;
+
+		for (int step = 0; step < amount; step++){
+			head += d;
+			updateTail();
+			visited.insert({rope.back()->x, rope.back()->y});
+		}
+	}
+
+	return to_string(visited.size());
+}
+
+vector<Day09::Move> Day09::parseMoves() {
+	vector<Move> moves;
+
+	for (const string &line : input){
+		Direction d(0, 0);
+		switch (line[0]) {
+			case 'L':
+				d.x = -1;
+				break;
+			case 'R':
+				d.x = 1;
+				break;
+			case 'U':
+				d.y = 1;
+				break;
+			case 'D':
+				d.y = -1;
+				break;
+		}
+		int amount = stoi(line.substr(2));
+		moves.emplace_back(d, amount);
+	}
+
+	return moves;
+}
+
+Day09::Vector Day09::Vector::operator+(Vector v2) const {
+	return {x + v2.x, y + v2.y};
+}
+
+void Day09::Vector::operator+=(Vector v2) {
+	x += v2.x;
+	y += v2.y;
 }

src/days/09/Day09.h

@@ -3,8 +3,23 @@
 #include "../../Day.h"
 
 class Day09 : public Day {
+	struct Vector {
+		Vector() = default;
+		Vector(int x, int y) : x(x), y(y) {};
+		int x {}; int y {};
+		Vector operator+ (Vector v2) const;
+		void operator+= (Vector v2);
+	};
+
+	typedef pair<int, int> PositionS;
+	typedef Vector Position;
+	typedef Vector Direction;
+	typedef pair<Direction, int> Move;
+
 protected:
 	Result Task1() override;
 
 	Result Task2() override;
+
+	vector<Move> parseMoves();
 };