1 files changed, 28 insertions, 0 deletions
diff --git a/codechef/binxor.py b/codechef/binxor.py
new file mode 100755
index 0000000..6f87d56
--- /dev/null
+++ b/codechef/binxor.py
@@ -0,0 +1,28 @@
+#!/usr/bin/env python3
+from functools import reduce
+from itertools import accumulate
+from typing import Iterable, Iterator
+
+MOD = 1_000_000_007
+LENGTH = 100_001
+
+
+def add(x: int, y: int) -> int: return (x + y) % MOD
+def mul(x: int, y: int) -> int: return x * y % MOD
+
+
+def khalid(iterable: Iterable[int]) -> Iterator[int]:
+    yield 1
+    yield from iterable
+
+
+modinv = [pow(i, MOD-2, MOD) for i in range(1, LENGTH)]
+facinv = tuple(khalid(accumulate(modinv, mul)))
+fac = tuple(khalid(accumulate(range(1, LENGTH), mul)))
+
+for t in range(int(input())):
+    n = int(input())
+    a, b = (min(b.count(c) for c in '01')
+            for b in (input() for i in range(2)))
+    print(reduce(add, (mul(mul(fac[n], facinv[i]), facinv[n - i])
+                       for i in range(abs(a-b), a+b+1, 2))))