# balanced.py -rw-r--r-- 1.1 KiB View raw 
                                                                                
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
def balanced(brackets: str) -> bool:
    closing_brackets = (")", "]", "}")
    opening_brackets = ("(", "[", "{")
    checks = {
        open_brace: close_brace
        for open_brace, close_brace in zip(opening_brackets, closing_brackets)
    }
    if not brackets or brackets in closing_brackets:
        return False
    stack = []
    for bracket in brackets:
        if bracket in opening_brackets:
            stack.append(bracket)
        elif bracket in closing_brackets and stack:
            if checks[stack[-1]]:
                stack.pop()
        else:
            return False
    return True if not stack else False


TESTS = [
    ("(", False),
    (")", False),
    ("()", True),
    ("(())", True),
    ("(()))", False),
    ("[", False),
    ("]", False),
    ("[]", True),
    ("[[]]", True),
    ("[[]]]", False),
    ("{", False),
    ("}", False),
    ("{}", True),
    ("{{}}", True),
    ("{{}}}", False),
    ("[(])", False), # TODO: This fails.
]


def run_tests() -> None:
    for given, expected in TESTS:
        assert balanced(given) == expected, (given, expected)


run_tests()