From ba7381b531a4306ec3310e135d6e1c84eb7d6e66 Mon Sep 17 00:00:00 2001
From: Benjo <benjamin.kraft@online.de>
Date: Tue, 21 Dec 2021 10:29:10 +0100
Subject: [PATCH] day 21

---
 21/21.py     | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 21/input     |  2 ++
 21/testInput |  2 ++
 3 files changed, 61 insertions(+)
 create mode 100644 21/21.py
 create mode 100644 21/input
 create mode 100644 21/testInput

diff --git a/21/21.py b/21/21.py
new file mode 100644
index 0000000..9a9a469
--- /dev/null
+++ b/21/21.py
@@ -0,0 +1,57 @@
+from itertools import product
+
+
+def readStartPositions(fileName):
+	with open(fileName) as file:
+		return tuple(int(line[len(line) - 1]) for line in file.read().splitlines())
+
+
+def part1(p1: int, p2: int):
+	P = {True: p1, False: p2}
+	S = {True: 0, False: 0}
+	p = True
+	totalDiceCount = 0
+	while True:
+		diceAmount = 0
+		for _ in range(3):
+			diceAmount += (totalDiceCount % 100) + 1
+			totalDiceCount += 1
+		P[p] += diceAmount
+		P[p] = ((P[p] - 1) % 10) + 1
+		S[p] += P[p]
+		if S[p] >= 1000:
+			break
+		p = not p
+	print(totalDiceCount * S[not p])
+
+
+cache = {}
+
+
+def part2(p1, p2, s1=0, s2=0, p=True):
+	if (p1, p2, s1, s2, p) in cache:
+		return cache[(p1, p2, s1, s2, p)]
+
+	winCount = {True: 0, False: 0}
+
+	for r1, r2, r3 in product([1, 2, 3], repeat=3):
+		P = {True: p1, False: p2}
+		S = {True: s1, False: s2}
+
+		P[p] += r1 + r2 + r3
+		P[p] = ((P[p] - 1) % 10) + 1
+		S[p] += P[p]
+		if S[p] >= 21:
+			winCount[p] += 1
+		else:
+			subWinCount = part2(*P.values(), *S.values(), not p)
+			winCount[True] += subWinCount[True]
+			winCount[False] += subWinCount[False]
+
+	cache[(p1, p2, s1, s2, p)] = winCount
+	return winCount
+
+
+startPos = readStartPositions("input")
+part1(*startPos)
+print(max(part2(*startPos).values()))
diff --git a/21/input b/21/input
new file mode 100644
index 0000000..ccc302a
--- /dev/null
+++ b/21/input
@@ -0,0 +1,2 @@
+Player 1 starting position: 1
+Player 2 starting position: 3
diff --git a/21/testInput b/21/testInput
new file mode 100644
index 0000000..3f69194
--- /dev/null
+++ b/21/testInput
@@ -0,0 +1,2 @@
+Player 1 starting position: 4
+Player 2 starting position: 8