Finding longest overlapping ranges [duplicate]

I think you can sort your input by the start of the ranges, then iterate through them. At each item, it is either added to the current range (if the start is less than the end of the current range) or we yield out current range and begin accumulating a new range:

def overlaps(ranges):
    ranges = sorted(ranges)  # If our inputs are garunteed sorted, we can skip this
    it = iter(ranges)
    try:
        curr_start, curr_stop = next(it)
        # overlaps = False  # If we want to exclude output ranges not produced by overlapping input ranges
    except StopIteration:
        return
    for start, stop in it:
        if curr_start <= start <= curr_stop:  # Assumes intervals are closed
            curr_stop = max(curr_stop, stop)
            # overlaps = True
        else:
            # if overlaps:
            yield curr_start, curr_stop
            curr_start, curr_stop = start, stop
            # overlaps = False
    # if overlaps:
    yield curr_start, curr_stop

print(list(overlaps([(1, 50), (49, 70), (75, 85), (84, 88), (87, 92)])))
# [(1, 70), (75, 92)]

print(list(overlaps([(20, 30), (5, 10), (1, 7), (12, 21)])))
# [(1, 10), (12, 30)]