chore: create new project structure and aoc.py runner script

adventofcode/2020/day11/rules.py

@@ -0,0 +1,117 @@
+#!/usr/bin/env python3
+from itertools import count, takewhile
+
+directions = (
+    (-1, -1),
+    (-1, 0),
+    (-1, 1),
+    (0, -1),
+    (0, 1),
+    (1, -1),
+    (1, 0),
+    (1, 1),
+)
+
+grid_width = 98
+grid_height = 97
+
+
+def handle_empty(index, grid, next_grid):
+    """
+    If a seat is empty (L) and there are no occupied seats adjacent to it, the seat becomes occupied.
+    """
+    neighbors = count_neighbors(index, grid)
+    if neighbors == 0:
+        next_grid[index] = "#"
+        return 1
+    return 0
+
+
+def handle_occupied(index, grid, next_grid):
+    """
+    If a seat is occupied (#) and four or more seats adjacent to it are also occupied, the seat becomes empty.
+    """
+    neighbors = count_neighbors(index, grid)
+    if neighbors >= 4:
+        next_grid[index] = "L"
+        return 1
+    return 0
+
+
+def count_neighbors(pos, grid):
+    neighbors = 0
+    x = pos % grid_width
+    y = pos // grid_width
+    for (dx, dy) in directions:
+        xx = x + dx
+        yy = y + dy
+        if not in_bounds((xx, yy)):
+            continue
+
+        if grid[yy * grid_width + xx] == "#":
+            neighbors += 1
+    return neighbors
+
+
+def handle_empty_2(index, grid, next_grid):
+    """
+    If a seat is empty and there are no occupied seat visible in neither direction,
+    the seat becomes occupied
+    """
+    neighbors = 0
+    x = index % grid_width
+    y = index // grid_width
+    for direction in directions:
+        # keep moving in the specified direction, while checking
+        # that we are in bounds of the grid
+        for xx, yy in takewhile(in_bounds, move(x, y, direction)):
+            cell = grid[yy * grid_width + xx]
+            if cell == "#":
+                neighbors += 1
+            elif cell == "L":
+                break  # No occupied seat in that direction, we can break
+
+    if neighbors == 0:
+        next_grid[index] = "#"
+        return True
+    return False
+
+
+def handle_occupied_2(index, grid, next_grid):
+    """
+    An occupied seat becomes empty if there are five or more visible occupied
+    seats in either direction.
+    """
+    occupied = 0
+    x = index % grid_width
+    y = index // grid_width
+    for direction in directions:
+        for xx, yy in takewhile(in_bounds, move(x, y, direction)):
+            cell = grid[yy * grid_width + xx]
+            if cell == "#":
+                occupied += 1
+            elif cell != ".":
+                break
+
+    if occupied >= 5:
+        next_grid[index] = "L"
+        return True
+    return False
+
+
+def in_bounds(pos):
+    x, y = pos
+    return 0 <= x < grid_width and 0 <= y < grid_height
+
+
+def move(x, y, direction):
+    xx = x
+    yy = y
+    while True:
+        yield xx, yy
+        xx += direction[0]
+        yy += direction[1]
+
+
+part1_rules = {"L": handle_empty, "#": handle_occupied}
+part2_rules = {"L": handle_empty_2, "#": handle_occupied_2}