day 11 & day 12

2024/day11/day11a.py

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+from functools import cache
+from sys import argv
+ 
+MAX_DEPTH = 75
+ 
+ 
+def parse(src):
+    '''Convert the input to a list of integers.'''
+    return [int(x) for x in src.split()]
+ 
+ 
+def count_digits(num):
+    '''Count the digits of num in base 10'''
+    total = 0
+    while num > 0:
+        total += 1
+        num = num // 10
+    return total
+ 
+ 
+@cache
+def expand(stone, depth=0):
+    '''Traverse the 'timeline' depth-first and return the number of stones
+       created by blinking at stone from depth to MAX_DEPTH blinks.'''
+    while depth < MAX_DEPTH:
+        if stone == 0:
+            stone = 1
+            depth += 1
+            continue
+ 
+        digits = count_digits(stone)
+        if digits % 2 == 0:
+            mask = 10 ** (digits // 2)
+            left = stone // mask
+            right = stone % mask
+ 
+            return expand(left, depth + 1) + expand(right, depth + 1)
+ 
+        stone *= 2024
+        depth += 1
+ 
+    return 1
+ 
+ 
+def main(stones):
+    '''The total number of stones produced after 75 blinks'''
+    return sum(expand(stone) for stone in stones)
+ 
+ 
+if __name__ == '__main__':
+    # pass the path to the puzzle input as the first argument
+    print(main(parse(open('/home/bandeira/git.bandeira/aoc/2024/day11/input.day11').read())))

2024/day11/input.day11

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+0 89741 316108 7641 756 9 7832357 91

2024/day11/sample.day11

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+125 17