0

Given a list of lists of positive integers, output a subset of them so their union forms a continuous non-empty range with no numbers missing. For example, consider this input:
[
[1, 2, 3, 5],
[2, 4, 6],
[7, 9, 11]
]
The union of the first 2 forms a continuous sequence: [1, 2, 3, 4, 5, ...