Gas Station

There are N gas stations along a circular route, where the amount of gas at station i is gas[i].

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.

public class Solution {
    public int canCompleteCircuit(int[] gas, int[] cost) {
        int N = gas.length;
        int j = 0;
        for(int i=0;i<N;i=j+1) {
            int sum = 0;
            for(j=i;j<N+i;j++) {
                sum = sum+gas[j%N];
                if(sum<cost[j%N]) break;
                else sum = sum-cost[j%N];
                if(j==N+i-1) return i;
            }
        }
        return -1;
    }
}