Pather Script | Python Fiddle

#!/usr/bin/python

# ETHAN NEFF
# 2014.23.01

# PROBLEM
# Given that the text file 'input.txt' contains a rectangular block of dot
# characters ('.') and two or more hash characters ('#'), write a program 'pather'
# which writes out to 'output.txt' the same data with the two '#' characters
# joined by asterisks ('*'). The command will be invoked like this:

# VISION
'''
cat input.txt
........................
........................
....#...................
........................
........................
........................
........................
..................#.....
........................
........................
........................
........................

python pather.py input.txt output.txt

cat output.txt
........................
........................
....#...................
....*...................
....*...................
....*...................
....*...................
....**************#.....
........................
........................
........................
........................
'''

# CRITERIAS
# 1 the program will not make any diagonals
# 2 the program will only change direction once
# 3 the program starts with a vertical line and then complete with a horizontal line

# ASSUMPTIONS
# 1 the program parses found hashtags from the top-left to the bottom-right
# 2 the program makes the connection to the next sequential hashtag (not based on shortest distances)
# 2 the program has strict argument inputs (programName inputFile outputFile)
# 4 the program will overwrite the output file

# HOW TO USE (command line)
# python pather.py input.txt output.txt

import sys

# initial argument check
if len(sys.argv) != 3:
	print "ERROR. Proper argument format: python pather.py inputFile.txt outputFile.txt"
	sys.exit()

# 2D array to store the output file
outputArray = []

# dictionary to store the found hashtags [y,x]
hashDict = {}

# READ THE INPUT FILE
try:
	inputFile = open(sys.argv[1], 'r')
except:
	print "ERROR. Could not read input file."
	sys.exit()

# LOCATE THE HASHTAGS
hashCount = 0;
lineCount = 0;
for line in inputFile:
	# clean the line
	line = line.rstrip('\n' ' ')

# parse individual line characters
	charCount = 0
	outputLine = []
	for i in range(0,len(line)):
		outputLine.append(line[i])
		if (line[i] == "#"):
			# find the hashes, and store their y and x coordinates in a dictionary
			hashDict[hashCount] = [lineCount,charCount]
			hashCount += 1
		charCount += 1
	lineCount += 1
	outputArray.append(outputLine)
inputFile.close()

# FILL IN ASTERISKS INBETWEEN HASHTAGS
if (len(hashDict) > 1):
	# go through each hashtag, and find the path to the next hashtag
	for i in range(0,len(hashDict)-1):
		# go vertical
		if (hashDict[i][0] != hashDict[i+1][0]):
			smallerY = hashDict[i+1][0]+1
			largerY = hashDict[i][0]+1
			if (smallerY > largerY):
				smallerY = hashDict[i][0]+1
				largerY = hashDict[i+1][0]+1
			for j in range(smallerY,largerY):
				outputArray[j][hashDict[i][1]] = '*'

# then horizontal
		smallerX = hashDict[i+1][1]+1
		largerX = hashDict[i][1]
		if (smallerX > largerX):
			smallerX = hashDict[i][1]+1
			largerX = hashDict[i+1][1]
		for j in range(smallerX,largerX):
			outputArray[hashDict[i+1][0]][j] = '*'

# WRITE THE OUTPUT FILE
outputFile = open(sys.argv[2], "w")
for line in outputArray:
	outputFile.write("".join(line) + "\n")
outputFile.close()

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