17

1 files changed, 85 insertions, 0 deletions

diff --git a/17.py b/17.py
new file mode 100644
index 0000000..8686ea8
--- /dev/null
+++ b/17.py
@@ -0,0 +1,85 @@
+from utils import open_day, Point2D as P
+from itertools import repeat, cycle
+
+pieces = [
+    { P(0, 0), P(1, 0), P(2, 0), P(3, 0) },
+    { P(1, 0), P(0, 1), P(1, 1), P(2, 1), P(1, 2) },
+    { P(0, 0), P(1, 0), P(2, 0), P(2, 1), P(2, 2) },
+    { P(0, 0), P(0, 1), P(0, 2), P(0, 3) },
+    { P(0, 0), P(1, 0), P(0, 1), P(1, 1) },
+]
+
+class Tower:
+    def __init__(self, width=7):
+        self.width = width
+        self.tower = []
+    @property
+    def height(self):
+        return len(self.tower) // self.width
+    def __str__(self):
+        rows = []
+        for y in range(self.height - 1, -1, -1):
+            rows.append('|' + ''.join(
+                    '#' if self.tower[y * self.width + x] else '.'
+                    for x in range(self.width)) + '|')
+        return '\n'.join(rows + ['+' + '-' * self.width + '+'])
+    def __setitem__(self, key, value):
+        if self.height <= key.y:
+            needed = self.width * (key.y - self.height + 1)
+            self.tower.extend(repeat(False, needed))
+        self.tower[key.y * self.width + key.x] = value
+    def __getitem__(self, key):
+        if key.x < 0 or key.x >= self.width or key.y < 0: raise IndexError
+        try: return self.tower[key.y * self.width + key.x]
+        except IndexError: return False
+    def get(self, key, default=None):
+        try: return self[key]
+        except IndexError: return default
+
+def place_piece(tower, origin, piece):
+    for offset in piece:
+        tower[origin + offset] = True
+
+def piece_fits(tower, origin, piece):
+    for offset in piece:
+        if tower.get(origin + offset, True): return False
+    return True
+
+with open_day(17) as f:
+    conv = { '<': -1, '>': 1 }
+    gusts = [conv[c] for c in f.read().rstrip()]
+
+def solve(gusts, cycles=2022):
+    tower = Tower()
+    it_gusts_i = cycle(range(len(gusts)))
+    gust_i = len(gusts) - 1
+    states = {}
+    heights = []
+    for piece_i, i in zip(cycle(range(len(pieces))), range(cycles)):
+        piece = pieces[piece_i]
+        pos = P(2, tower.height + 3)
+        for gust_i in it_gusts_i:
+            gust = gusts[gust_i]
+            nextpos = pos + P(gust, 0)
+            if piece_fits(tower, nextpos, piece):
+                pos = nextpos
+            nextpos = pos + P(0, -1)
+            if not piece_fits(tower, nextpos, piece):
+                break
+            pos = nextpos
+        place_piece(tower, pos, piece)
+        top_row = sum(1 << x if tower.get(P(x, tower.height-1), True) else 0 for x in range(tower.width))
+        state_key = (top_row, piece_i, gust_i)
+        if state_key in states: break
+        states[state_key] = i, tower.height
+        heights.append(tower.height)
+    else: return tower.height
+    base_i, base_height = states[state_key]
+    cycle_len = i - base_i
+    cycle_height = tower.height - base_height
+    height = (cycles - base_i) // cycle_len * cycle_height
+    height += heights[(cycles - 1) % cycle_len]
+    return height
+
+print(solve(gusts))
+print(solve(gusts, 1000000000000))