## find missing ranges between low and high in the given array.
# ex) [3, 5] lo=1 hi=10 => answer: [1->2, 4, 6->10]

def missing_ranges(nums, lo, hi):
    res = []
    start = lo
    for num in nums:
        if num < start:
            continue
        if num == start:
            start += 1
            continue
        res.append(get_range(start, num-1))
        start = num + 1
    if start