def merge(list1, list2):
    """ Given two sorted lists, return sorted collection of both
        >>> merge([1, 1, 3], [1, 1])
    """
    (i1, i2) = (0, 0)
    result = []
    while len(result) < len(list1) + len(list2):
        if list1[i1] < list2[i2]:   # COULD CRASH
            result.append(list1[i1])
            if i1 < len(list1):
                i1 += 1
        else:
            result.append(list2[i2])
            if i2 < len(list2):
                i2 += 1
    return result

def merge2(list1, list2):
    """ Given two sorted lists, return sorted collection of both
        >>> merge([1, 1, 3], [1, 1])
    """
    (i1, i2) = (0, 0)
    result = []
    while i2 < len(list2) and i1 < len(list1):
        if list1[i1] < list2[i2]:
            result.append(list1[i1])
            i1 += 1
        else:
            result.append(list2[i2])
            i2 += 1
    # One of the originals isn't empty, so copy the rest over.
    if i2 >= len(list2):
        while i1 < len(list1):
            result.append(list1[i1])
            i1 += 1
    else:
        while i2 < len(list2):
            result.append(list2[i2])
            i2 += 1
    return result


def mergesort(array):
    """ Return sorted array """
    # NOT in place
    return []

def main():
    import random
    numbers = range(10)
    random.shuffle(numbers)
    print "original : " + str(numbers)
    numbers = mergesort(numbers)
    print "sorted   : " + str(numbers)

if __name__ == "__main__":
    import doctest
    doctest.testmod()
    main()