--description--

For the breadth-first search approach, you'll use a queue to track different states as you build the parentheses combinations. Each state will be represented as a tuple containing three elements:

• The current string being built
• The number of opening parentheses used so far
• The number of closing parentheses used so far

Create a variable named queue and initialize it with a list containing one tuple: ('', 0, 0). This represents the starting state with an empty string and zero parentheses used.

--hints--

You should declare a variable named queue in your gen_parentheses function.

({ test: () => runPython(`
assert _Node(_code).find_function("gen_parentheses").has_variable("queue")
`) })

You should initialize queue with a list containing the tuple ('', 0, 0).

({ test: () => runPython(`
assert _Node(_code).find_function("gen_parentheses").find_variable("queue").is_equivalent("queue = [('', 0, 0)]")
`) })

--seed--

--seed-contents--

--fcc-editable-region--
def gen_parentheses(pairs):
    if not isinstance(pairs, int):
        return 'The number of pairs should be an integer'
    if pairs < 1:
        return 'The number of pairs should be at least 1'
    
    result = []
    return result
--fcc-editable-region--