There are N gas stations along a circular route, where the amount of gas at station i is
You have a car with an unlimited gas tank and it costs
cost[i] of gas to travel from station i to its next station (i+1). You begin the journey with an empty tank at one of the gas stations.
Return the starting gas station's index if you can travel around the circuit once, otherwise return -1.
The solution is guaranteed to be unique.