Implemented 2017 Day 22 Part 2

Author: SimonBaars

src/main/java/com/sbaars/adventofcode/year17/days/Day22.java

@@ -8,6 +8,10 @@ public class Day22 extends Day2017 {
     private static final int RIGHT = 1;
     private static final int DOWN = 2;
     private static final int LEFT = 3;
+    private static final int CLEAN = 0;
+    private static final int WEAKENED = 1;
+    private static final int INFECTED = 2;
+    private static final int FLAGGED = 3;
 
     private static class Point {
         int x, y;
@@ -91,6 +95,57 @@ public Object part1() {
 
     @Override
     public Object part2() {
-        return 0;
+        String[] grid = dayStrings();
+        Map<Point, Integer> nodes = new HashMap<>();
+
+        // Parse initial grid
+        int centerY = grid.length / 2;
+        int centerX = grid[0].length() / 2;
+        for (int y = 0; y < grid.length; y++) {
+            for (int x = 0; x < grid[y].length(); x++) {
+                if (grid[y].charAt(x) == '#') {
+                    nodes.put(new Point(x - centerX, y - centerY), INFECTED);
+                }
+            }
+        }
+
+        // Start virus carrier at center facing up
+        Point carrier = new Point(0, 0);
+        int direction = UP;
+        int infections = 0;
+
+        // Simulate 10000000 bursts
+        for (int burst = 0; burst < 10000000; burst++) {
+            int currentState = nodes.getOrDefault(carrier, CLEAN);
+
+            // Turn based on current node state
+            switch (currentState) {
+                case CLEAN -> direction = (direction + 3) % 4;  // Turn left
+                case INFECTED -> direction = (direction + 1) % 4;  // Turn right
+                case FLAGGED -> direction = (direction + 2) % 4;  // Reverse
+                // WEAKENED: Don't turn
+            }
+
+            // Update node state
+            int newState = (currentState + 1) % 4;
+            if (newState == INFECTED) {
+                infections++;
+            }
+            if (newState == CLEAN) {
+                nodes.remove(carrier);
+            } else {
+                nodes.put(new Point(carrier.x, carrier.y), newState);
+            }
+
+            // Move forward
+            switch (direction) {
+                case UP -> carrier.y--;
+                case RIGHT -> carrier.x++;
+                case DOWN -> carrier.y++;
+                case LEFT -> carrier.x--;
+            }
+        }
+
+        return infections;
     }
 }