day 7, easy recursion

d07/run.py

@@ -0,0 +1,30 @@
+import sys
+from math import *
+
+PART2 = len(sys.argv)>1 and sys.argv[1] == "2"
+I = sys.stdin.read().strip().split("\n")
+
+def conccat(a, b):
+    # 12 345 become 12345
+    # return a * pow(10, ceil(log10(b))) + b <= breaksfor 1000
+    # but int <-> str convertions are slow (x4)
+    return int(str(a)+str(b))
+
+def gen_nb(L:list[int]):
+    if len(L) == 1:
+        yield L[0]
+    else:
+        for x in gen_nb(L[:-1]):
+            yield L[-1] * x
+            yield L[-1] + x
+            if PART2:
+                yield conccat(x, L[-1])
+
+S = 0
+for l in I:
+    r, nb = l.split(":")
+    x = int(r)
+    nb = list(map(int,nb.strip().split(" ")))
+    S += x * any(x == a for a in gen_nb(nb))
+print(S)
+