A quick implementation of algorithms in gas stations

gasoptimize.py

class Gas():
	"""Gas lookup optimization"""
	def __init__(self, gas, cost):
		self.gas = gas
		self.cost = cost
	def canCompleteCircuit(self):
		n = len(self.gas)
		start = 0
		total = 0
		tank = 0

		for i in range(0, n):
			dif =  self.gas[i] - self.cost[i]
			tank += dif       # extra fuel in tank
			total += dif
			if (tank < 0):
				start = i + 1 # should start from next
				tank = 0      # empty the tank

		# if total cost is larger than total gas, then impossible
		return -1 if total < 0 else start

checkStations = Gas([100,10,56], [200, 400, 500])
print (checkStations.canCompleteCircuit())