day 22

2020/22/22.py

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+with open("input_sample.txt") as f:
+	p1, p2 = f.read().split('\n\n')
+	p1 = p1.split('\n')[1:]
+	p2 = p2.split('\n')[1:]
+	p1 = list(map(int, p1))
+	p2 = list(map(int, p2))
+	
+i = 1
+while True:
+	#print(f"-- Round {i} --")
+	#print("Player 1's deck: ", p1)
+	#print("Player 2's deck: ", p2)
+	c1 = p1.pop(0)
+	c2 = p2.pop(0)
+	#print("Player 1 plays: ",c1)
+	#print("Player 2 plays: ",c2)
+	if c1 > c2:
+		#print("Player 1 wins the round!")
+		p1 += [c1, c2]
+	else:
+		#print("Player 2 wins the round!")
+		p2 += [c2, c1]
+	i += 1
+	#print(p1,p2)
+	if len(p1) == 0:
+		winner = p2
+		break
+	if len(p2) == 0:
+		winner = p1
+		break
+part1 = 0
+for i, card in enumerate(reversed(winner)):
+	part1 += (i+1)*card
+print(part1)
+
+with open("input.txt") as f:
+	p1, p2 = f.read().split('\n\n')
+	p1 = p1.split('\n')[1:]
+	p2 = p2.split('\n')[1:]
+	p1 = list(map(int, p1))
+	p2 = list(map(int, p2))
+
+def play(p1, p2):
+	seen = set()
+	while True:
+		# does p1 auto-win?
+		state = (tuple(p1), tuple(p2))
+		if state in seen:
+			return 1, p1
+		seen.add(state)
+		# draw cards
+		c1 = p1.pop(0)
+		c2 = p2.pop(0)
+		# should we recurse?
+		if len(p1) >= c1 and len(p2) >= c2: # play recursive round
+			winner, deck = play(p1[:c1],p2[:c2]) # copy that many cards
+			if winner == 1:
+				p1 += [c1, c2]
+			else: # winner == 2
+				p2 += [c2, c1]
+		else: # play normal round
+			if c1 > c2:
+				p1 += [c1, c2]
+			else: # c2 > c1
+				p2 += [c2, c1]
+		# does anyone win by normal rules?
+		if len(p1) == 0:
+			return 2, p2
+			break
+		if len(p2) == 0:
+			return 1, p1
+
+i, winner = play(p1, p2)
+
+part2 = 0
+for i, card in enumerate(reversed(winner)):
+	part2 += (i+1)*card
+print(part2)

2020/22/input.txt

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+Player 1:
+44
+47
+29
+31
+10
+40
+50
+27
+35
+30
+38
+11
+14
+9
+42
+1
+26
+24
+6
+13
+8
+15
+21
+18
+4
+
+Player 2:
+17
+22
+28
+34
+32
+23
+3
+19
+36
+12
+45
+37
+46
+39
+49
+43
+25
+33
+2
+41
+48
+7
+5
+16
+20

2020/22/input_sample.txt

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+Player 1:
+9
+2
+6
+3
+1
+
+Player 2:
+5
+8
+4
+7
+10