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curriculum/challenges/english/blocks/workshop-breadth-first-search/68e00c5349cbddfef6dbc053.md

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--description--

Inside your while loop, use queue.pop(0) to remove and get the first element from the queue. This implements the first-in-first-out (FIFO) behavior characteristic of BFS.

Unpack this tuple into three variables: current, opens_used, and closes_used.

--hints--

You should use queue.pop(0) to get the first element from the queue.

js
({ test: () => runPython(`
assert "queue.pop(0)" in str(_Node(_code).find_function("gen_parentheses").find_whiles()[0].find_bodies()[0])
`) })

You should unpack the result into three variables: current, opens_used, and closes_used.

js
({ test: () => runPython(`
assert _Node(_code).find_function("gen_parentheses").find_whiles()[0].find_bodies()[0].has_stmt("current, opens_used, closes_used = queue.pop(0)")
`) })

--seed--

--seed-contents--

py
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'
    
    queue = [('', 0, 0)]
    result = []
--fcc-editable-region--
    while queue:
        print(queue)
        
--fcc-editable-region--
    return result