Day 23

2020/day23.py

@@ -0,0 +1,51 @@
+import sys
+
+def main():
+    lines = [line.rstrip() for line in sys.stdin]
+
+    # Part 1
+    cups = list(map(int, lines[0]))
+    for _ in range(100):
+        move(cups)
+    while cups[0] != 1:
+        cups.append(cups.pop(0))
+    print("Part 1:", "".join(map(str, cups))[1:])
+
+    # Part 2
+    # No spare 256TB of RAM nor repetitions it seems! Use another structure.
+    cups_list = list(map(int, lines[0]))
+    cups_list += list(range(10, 1000001))
+    cups = {
+        cups_list[i]: cups_list[(i + 1) % 1000000]
+        for i in range(len(cups_list))
+    }
+    cc = cups_list[0]
+    for _ in range(10000000):
+        zyoooom(cups, cc)
+        cc = cups[cc]
+    print("Part 2:", cups[1] * cups[cups[1]])
+
+def move(cups):
+    cc = cups[0]
+    pick = cups[1:4]
+    d = cc - 1 or 9
+    while d in pick:
+        d = d - 1 if d > 1 else 9
+    del cups[1:4]
+    di = cups.index(d) + 1
+    cups[di:di] = pick
+    cups.append(cups.pop(0))
+
+def zyoooom(cups, c):
+    pick = cups[c], cups[cups[c]], cups[cups[cups[c]]]
+    after_pick = cups[pick[2]]
+    dest = c - 1 or 1000000
+    while dest in pick:
+        dest = dest - 1 if dest > 1 else 1000000
+    after_dest = cups[dest]
+    cups[c] = after_pick
+    cups[dest] = pick[0]
+    cups[pick[2]] = after_dest
+
+if __name__ == "__main__":
+    main()