Quick little algorithm to chop up an array into an array of contiguous ranges.

segment.py

samples=[
    # =======================================
    # input, expected result pairs
    # =======================================
    # empty list
    ([], []),
    # single digit
    ([1], [(1,1)]),
    # basic range
    ([1,2,3], [(1,3)]),
    # should handle duplicates
    ([1,2,3,2], [(1,3)]),
    # order shouldn't matter
    ([3,2,1], [(1,3)]),
    # basic two ranges
    ([1,2,3,6,7,8], [(1,3),(6,8)]),
    # multiple ranges and single digits
    ([1,2,3,5,7,8,11], [(1,3),(5,5),(7,8),(11,11)]),
    # bunch of single digits
    ([1,5,10], [(1,1), (5,5), (10,10)]),
    ]

def segment(array):
    """
    Segment an array of numbers into continguous ranges.      """
    if len(array) ==0: return []
    array.sort()
    result=[]
    mark_low = array[0]
    mark_high = array[0]
    for v in array:
        if v-mark_high > 1:
            result.append((mark_low, mark_high))
            mark_low=v
            mark_high=v
        else:
            mark_high=v
    result.append((mark_low, mark_high))
    return result
            

for tInput, tResult in samples:
    result = segment(tInput)
    if tResult != result:
        print "Error: %s => %s (expected %s)" % (tInput, result, tResult)