1c_zigzag.py

import unittest
 
def zigzag(cs, num_rows):
	"""
	Authored by Dhruv - TA will be Dhruv.

	In order to encode text messages in a format that is unreadable to other, 
	Alice decides to create a cipher and wants a program to test it out on her 
	messages. The cipher (which is essentially an algorithm) rewrites a text 
	message, taken in as a string of contiguous characters, with the use of a 
	secret “key”, a constant num_rows.

	If the string taken in is "PAYPALISHIRING" and num_rows = 3, the string will 
	be rewritten as 

	P P I I N
	A A S R G
	Y L H I

	and the program should thus output “PPIINAASRGYLJI”.

	If num_rows = 4, the string will instead be written as

	P A H N 
	A L I G 
	Y I R
	P S I 

	and the program should thus output “PAHNALIGYIRPSI”.
	
	Write a function zigzag that takes as input a string and an integer 
	representing num_rows.
	"""

	# TODO: Fill up your code here, and set output to the final answer.
	output = None
	
	# This returns the final output string.
	return output 

class TestZigZag(unittest.TestCase):
	def test_zigzag(self):
		f = zigzag
		self.assertEqual(f('PAYPALISHIRING', 3), 'PPIINAASRGYLHI')
		self.assertEqual(f('PAYPALISHIRING', 4), 'PAHNALIGYIRPSI')
		self.assertEqual(f('SCRAMBLESCRABBLE', 4), 'SMSBCBCBRLRLAEAE')

if __name__ == '__main__':
	unittest.main()