2021 day 6

2021/06/06.py

@@ -0,0 +1,30 @@
+with open("sample.txt") as f:
+	fish = [int(n) for n in f.read().split(',')]
+
+def advance(fish):
+	tomorrow = []
+	spawn = 0
+	for f in fish:
+		if f == 0:
+			tomorrow.append(6)
+			spawn += 1
+		else:
+			tomorrow.append(f-1)
+	for i in range(spawn):
+		tomorrow.append(8)
+	return tomorrow
+
+def part1(fish):
+	for i in range(80):
+		fish = advance(fish)
+	return len(fish)
+
+print(part1(fish))
+
+## TOO LONG
+# def part2(fish):
+# 	for i in range(256):
+# 		fish = advance(fish)
+# 	return len(fish)
+
+# print(part2(fish))

2021/06/06_refactored.py

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+with open("sample.txt") as f:
+	fish = [int(n) for n in f.read().split(',')]
+
+# note that we don't actually care about the timers themselves,
+# we just care about the total count after x days.
+# 
+# technically we also care about the timer values,
+# since this directly influences the total count per daily cycle.
+
+from collections import Counter
+
+def advance(counter, days):
+	for day in range(days):
+		counter[(day+7)%9] += counter[day%9] # every 7 days, a new fish spawns taking 9 days.
+	return sum(counter.values())
+
+c = Counter(fish)
+part1 = advance(c,80)
+c = Counter(fish)
+part2 = advance(c,256)
+print(part1, part2)

2021/06/input.txt

@@ -0,0 +1 @@
+1,1,5,2,1,1,5,5,3,1,1,1,1,1,1,3,4,5,2,1,2,1,1,1,1,1,1,1,1,3,1,1,5,4,5,1,5,3,1,3,2,1,1,1,1,2,4,1,5,1,1,1,4,4,1,1,1,1,1,1,3,4,5,1,1,2,1,1,5,1,1,4,1,4,4,2,4,4,2,2,1,2,3,1,1,2,5,3,1,1,1,4,1,2,2,1,4,1,1,2,5,1,3,2,5,2,5,1,1,1,5,3,1,3,1,5,3,3,4,1,1,4,4,1,3,3,2,5,5,1,1,1,1,3,1,5,2,1,3,5,1,4,3,1,3,1,1,3,1,1,1,1,1,1,5,1,1,5,5,2,1,5,1,4,1,1,5,1,1,1,5,5,5,1,4,5,1,3,1,2,5,1,1,1,5,1,1,4,1,1,2,3,1,3,4,1,2,1,4,3,1,2,4,1,5,1,1,1,1,1,3,4,1,1,5,1,1,3,1,1,2,1,3,1,2,1,1,3,3,4,5,3,5,1,1,1,1,1,1,1,1,1,5,4,1,5,1,3,1,1,2,5,1,1,4,1,1,4,4,3,1,2,1,2,4,4,4,1,2,1,3,2,4,4,1,1,1,1,4,1,1,1,1,1,4,1,5,4,1,5,4,1,1,2,5,5,1,1,1,5

2021/06/sample.txt

@@ -0,0 +1 @@
+3,4,3,1,2