day 8

day_08/part_a.py

@@ -0,0 +1,38 @@
+import aocd
+import collections
+
+def solve(data):
+    grid = collections.defaultdict(list)
+    antinodes = set()
+
+    rows = data.split('\n')
+    width = len(rows[0])
+    height = len(rows)
+
+    for y, row in enumerate(rows):
+        for x, cell in enumerate(row):
+            if cell == '.':
+                continue
+
+            for prev_x, prev_y in grid[cell]:
+                dx = x - prev_x
+                dy = y - prev_y
+
+                for potential in ((prev_x-dx, prev_y-dy), (x+dx, y+dy)):
+                    if 0 <= potential[0] < width and 0 <= potential[1] < height:
+                        antinodes.add(potential)
+            
+            grid[cell].append((x, y))
+    
+    return sum(1 for _ in antinodes)
+
+if __name__ == '__main__':
+    puz = aocd.models.Puzzle(year=2024, day=8)
+
+    # data = puz.examples[0].input_data
+    data = puz.input_data
+
+    solution = solve(data)
+
+    print(solution)
+    aocd.submit(solution, year=2024, day=8, part='a')

day_08/part_b.py

@@ -0,0 +1,53 @@
+import aocd
+import math
+import collections
+import itertools
+
+def solve(data):
+    grid = collections.defaultdict(list)
+    antinodes = set()
+
+    rows = data.split('\n')
+    width = len(rows[0])
+    height = len(rows)
+
+    for y, row in enumerate(rows):
+        for x, cell in enumerate(row):
+            if cell == '.':
+                continue
+
+            for prev_x, prev_y in grid[cell]:
+                dx = x - prev_x
+                dy = y - prev_y
+
+                angle = math.gcd(dx, dy)
+                dx, dy = dx // angle, dy // angle
+
+                # In the direction of the previous antenna...
+                for i in itertools.count(step=-1):
+                    if 0 <= (new_x := prev_x + dx*i) < width and 0 <= (new_y := prev_y + dy*i) < height:
+                        antinodes.add((new_x, new_y))
+                    else:
+                        break
+
+                # In the direction of the current antenna...
+                for i in itertools.count(step=1):
+                    if 0 <= (new_x := x + dx*i) < width and 0 <= (new_y := y + dy*i) < height:
+                        antinodes.add((new_x, new_y))
+                    else:
+                        break
+            
+            grid[cell].append((x, y))
+    
+    return sum(1 for _ in antinodes)
+
+if __name__ == '__main__':
+    puz = aocd.models.Puzzle(year=2024, day=8)
+
+    # data = puz.examples[0].input_data
+    data = puz.input_data
+
+    solution = solve(data)
+
+    print(solution)
+    aocd.submit(solution, year=2024, day=8, part='b')