fancy_pattern.py

import math
import sys
import unittest

# input : N positive integer, ex. N = 10
# output : sequence as list, ex. 1 2 * 3 4 5 * 6 7 * 8 9 10 *
def fancy_pattern(N):
    pattern = '11*111*' * int(math.ceil(N / 5.0))
    result = []
    n = 0
    i = 0
    while i < N:
        if pattern[n] == '1': 
            result.append(str(i+1))
            i += 1
        else: 
            result.append(pattern[n])
        n += 1

    # NOTE: append '*' if number appeare 2 / 3 times at the end of result after last '*'
    if ((N - 2) % 5) == 0 or (N % 5) == 0:
        result.append(pattern[len(pattern) - 1])

    return result

class TestSequence(unittest.TestCase):
    def test_fancy_pattern(self):
        expected = [['1'],
                    ['1', '2', '*'],
                    ['1', '2', '*', '3'],
                    ['1', '2', '*', '3', '4'],
                    ['1', '2', '*', '3', '4', '5', '*']]
        ok_cnt = 0
        len_data = len(expected)
        for i in range(1, len_data + 1):
            result = fancy_pattern(i)
            if result == expected[i-1]: 
                ok_cnt += 1

        self.assertEqual(ok_cnt, len_data)        


if __name__ == '__main__':

    if len(sys.argv) > 1 and sys.argv[1] == 'TestSequence':
        unittest.main()
        sys.exit()

    N = 1000
    result = fancy_pattern(N)

    if len(result) > 25:
        text = ' '.join(result[:21])
        text += ' ... %s' % ' '.join(result[len(result) - 2:])
    else:
        text = ' '.join(result)

    print text