[Leetcode] 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.

Note:
The solution is guaranteed to be unique.

Solution:

http://blog.csdn.net/kenden23/article/details/14106137

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