Solve 2021 day 20, 21, 23, 25

2021/d21.py

@@ -0,0 +1,65 @@
+from lib import get_data
+from lib import ints
+from collections import defaultdict
+
+
+FIELD = 10
+DICE = 100
+dice = -1
+
+data = get_data(__file__)
+
+_, p1, _, p2 = ints(data)
+pos = [p1 - 1, p2 - 1]
+scores = [0, 0]
+
+dice_rolls = 0
+not_done = True
+while not_done:
+    for p in range(len(scores)):
+        dice_rolls += 3
+        for _ in range(3):
+            dice += 1 % DICE
+            pos[p] = (pos[p] + (dice + 1)) % FIELD
+        scores[p] += pos[p] + 1
+        if scores[p] >= 1000:
+            not_done = False
+            break
+
+r = min(scores) * dice_rolls
+print(r)
+
+_, p1, _, p2 = ints(data)
+pos = (p1 - 1, p2 - 1)
+scores = (0, 0)
+unis = defaultdict(int)
+won = [0, 0]
+unis[(0, pos, scores)] += 1
+
+while unis:
+    nunis = defaultdict(int)
+    for (turn, opos, scores), count in unis.items():
+        other = (turn + 1) % 2
+        poss = [opos[turn]]
+        for _ in range(3):
+            nposs = []
+            for dice in range(1, 3 + 1):
+                for pos in poss:
+                    npos = (pos + dice) % FIELD
+                    nposs.append(npos)
+            poss = nposs
+
+        for npos_player in poss:
+            score = scores[turn] + npos_player + 1
+            if score >= 21:
+                won[turn] += count
+            else:
+                nscores = list(scores)
+                nscores[turn] = score
+                npos = list(opos)
+                npos[turn] = npos_player
+                state = (other, tuple(npos), tuple(nscores))
+                nunis[state] += count
+    unis = nunis
+
+print(max(won))