instance_validator.py

# Released to students

import sys

def main(argv):
	if len(argv) != 1:
                print "Usage: python instance_validator.py [path_to_input_file]"
                return
        print processInput(argv[0])

def processInput(s):
	fin = open(s, "r")
	line = fin.readline().split()
	if len(line) != 1 or not line[0].isdigit():
		return "Line 1 must contain a single integer."
	N = int(line[0])
	if N < 1 or N > 500:
		return "N must be an integer between 1 and 500, inclusive."

	line = fin.readline().split()
	if len(line) > N:
		return "There cannot be more than N children vertices."

	children = []
	for child in line:
		if not child.isdigit():
			return "The line of children must contain integers"
		child = int(child)
		if child < 0 or child >= N:
			return "Each child index must be between 0 and N-1"
		children.append(child)

	d = [[0 for j in range(N)] for i in range(N)]
	for i in xrange(N):
		line = fin.readline().split()
		if len(line) != N:
			return "Line " + str(i+2) + " must contain N integers."
		for j in xrange(N):
			if not line[j].isdigit():
				return "Line " + str(i+2) + " must contain N integers."
			d[i][j] = int(line[j])
			if d[i][j] < 0 or d[i][j] > 1:
				return "The adjacency matrix must be comprised of 0s and 1s."
	for i in xrange(N):
		if d[i][i] != 0:
			return "A node cannot have an edge to itself."
	return "instance ok"

if __name__ == '__main__':
	main(sys.argv[1:])