2020/13

toolkit.py

@@ -1,6 +1,7 @@
 import collections
 import hashlib
 import itertools
+import math
 import os
 import re
 import sys
@@ -9,6 +10,10 @@ from pathlib import Path
 import requests
 
 
+def lcm(a, b):
+    return abs(a * b) // math.gcd(a, b)
+
+
 def render(grid, brush=None):
     if brush is None:
         brush = {v: v for v in grid.values()}

y2020/p13.py

@@ -0,0 +1,26 @@
+import sys
+from itertools import count
+
+import toolkit
+
+
+text = sys.stdin.read()
+
+
+tid, string = text.split()
+tid = int(tid)
+found = [
+    next((tid + i, val) for i in count() if (tid + i) % val == 0)
+    for val in [int(v) for v in string.split(',') if v != 'x']
+]
+a, b = min(found)
+print((a - tid) * b)
+
+
+args = [(i, int(val)) for i, val in enumerate(string.split(',')) if val != 'x']
+(last, step), *tail = args
+for offset, value in tail:
+    i = next(i for i in count() if (last + i * step + offset) % value == 0)
+    last += i * step
+    step = toolkit.lcm(step, value)
+print(last)