Solve problem 106 in Python first 50% difficulty

python/e106.py

@@ -0,0 +1,44 @@
+def repeat(n, xs):
+    return [xs for _ in range(n)]
+
+
+def sequence(xss, acc):
+    if not xss:
+        return acc
+    return sequence(xss[1:], [a + [x] for x in xss[0] for a in acc])
+
+
+def is_balanced(xs):
+    """ Check if subsets are balanced. That means for every lower number there
+    is a higher number that balances it out. """
+    ones_balanced, twos_balanced = True, True
+    ones, twos = 0, 0
+    for x in xs:
+        if x == 1:
+            ones += 1
+            twos -= 1
+        elif x == 2:
+            ones -= 1
+            twos += 1
+        if ones < 0:
+            ones_balanced = False
+        if twos < 0:
+            twos_balanced = False
+    return ones_balanced or twos_balanced
+
+
+def euler_106():
+    n = 12
+    # Generate all possible subsets where both subsets have the same number of
+    # elements and at least two elements per subset.
+    xs = repeat(n, [0, 1, 2])
+    xs = [x for x in sequence(xs, [[]])
+          if x.count(1) > 1
+          if x.count(1) == x.count(2)]
+    return len([1 for x in xs if not is_balanced(x)]) // 2
+
+
+if __name__ == "__main__":
+    solution = euler_106()
+    print("e106.py: " + str(solution))
+    assert(solution == 21384)