Gas Station

只有一个答案，找到最后一个不可以的点，下一个是开始点

public class Solution {
    public int canCompleteCircuit(int[] gas, int[] cost) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        int total = 0;
        int sum = 0;
        int startindex = -1;
        for(int i = 0; i < gas.length; i++)
        {
            total += (gas[i] - cost[i]);
            sum += (gas[i] - cost[i]);
            if(sum < 0)
            {
                sum = 0;
                startindex = i;
            }
        }
        return total < 0? -1:startindex + 1;
    }
}