fix tolerance

splitbill.py

@@ -60,6 +60,8 @@ def solve(balances: dict[str, int], tolerance: int = 0) -> dict[tuple[str, str],
     possibilities = []
     for subgroup in zerosum_subgroups(balances, tolerance):
         balances_sub, balances_other = split_dict(balances, lambda k, v: k in subgroup)
+        if abs(sum(balances_other.values())) > tolerance:
+            continue
         transactions_sub = solve(balances_sub, tolerance)
         transactions_other = solve(balances_other, tolerance)
         possibilities.append(transactions_sub | transactions_other)

test.py

@@ -0,0 +1,19 @@
+import random
+from splitbill import solve, perform_transfers
+import pytest
+
+
+@pytest.mark.parametrize("tolerance", [0, 1, 2, 10, 100])
+def test_random(tolerance):
+    balances = {str(k): random.randint(-200, 200) for k in range(7)}
+    balances["7"] = -sum(balances.values())
+    balances = {k: v for k, v in balances.items() if v != 0}
+    transactions = solve(balances, tolerance)
+    assert abs(sum(perform_transfers(balances, transactions).values())) <= tolerance
+
+
+def test_bug1():
+    tolerance = 100
+    balances = {'0': -39, '1': 139, '2': -54, '3': 99, '4': 13, '5': 175, '6': -173, '7': -160}
+    transactions = solve(balances, tolerance=tolerance)
+    assert abs(sum(perform_transfers(balances, transactions).values())) <= tolerance