🍊

VERSION

@@ -1 +1 @@
-🚌
+🍊

y2023/p21.py

@@ -0,0 +1,27 @@
+text = open(0).read()
+graph = {
+    complex(x, y): val
+    for y, row in enumerate(text.splitlines())
+    for x, val in enumerate(row)
+}
+width = max(int(p.real) for p in graph) + 1
+height = max(int(p.imag) for p in graph) + 1
+
+wrap = lambda p: complex(p.real % width, p.imag % height)
+start, = (k for k, v in graph.items() if v == 'S')
+state = {(False, start)}
+seen = state.copy()
+for step in range(100):
+    state = {
+        (not age, p + s)
+        for age, p in state
+        for s in [1, -1, 1j, -1j]
+        if graph[wrap(p + s)] in {'.', 'S'}
+        if (not age, p + s) not in seen
+    }
+    seen |= state
+
+    if step == 64:
+        ans1 = sum(not age for age, pos in seen if pos in graph)
+        print(ans1)
+

y2023/p22.py

@@ -0,0 +1,49 @@
+@lambda fn: lambda brick: set(fn(brick))
+def dimension(brick):
+    (x1, x2), (y1, y2), (z1, z2) = map(sorted, zip(*brick))
+    for z in range(z1, z2 + 1):
+        for y in range(y1, y2 + 1):
+            for x in range(x1, x2 + 1):
+                yield x, y, z
+
+
+def tetris(bricks):
+    floor = {(x, y, 0) for x in range(100) for y in range(100)}
+    seen = floor
+    for brick in map(dimension, bricks):
+        while not seen & brick:
+            brick = {(x, y, z - 1) for x, y, z in brick}
+        resting_place = {(x, y, z + 1) for x, y, z in brick}
+        seen |= resting_place
+        yield resting_place
+
+
+def topple(i, depends_on, holds_up):
+    gone = set()
+    state = {i}
+    while state:
+        gone |= state
+        state = {above
+            for below in state
+            for above in depends_on.get(below, [])
+            if holds_up[above] <= gone
+        }
+    return gone - {i}
+
+
+text = open(0).read()
+bricks = [[[int(n) for n in sub.split(',')] for sub in line.split('~')] for line in text.splitlines()]
+bricks.sort(key=lambda brick: min(z for x, y, z in brick))
+bricks = list(tetris(bricks))
+
+known = {i for i, _ in enumerate(bricks)}
+holds_up, depends_on = {}, {}
+for j, brick in enumerate(bricks):
+    j_brick_1_down = {(x, y, z - 1) for x, y, z in brick}
+    holds_up[j] = {i for i, i_brick in enumerate(bricks) if i != j and j_brick_1_down & i_brick}
+    for i in holds_up[j]:
+        depends_on.setdefault(i, set()).add(j)
+
+needed = {v for k, vs in holds_up.items() if len(vs) == 1 for v in vs}
+print(len(known - needed))
+print(sum(len(topple(i, depends_on, holds_up)) for i in needed))