Gas Station

三年前找工作时应该做过这题，现在完全不记得了。

参考链接

public class Solution {
    public int canCompleteCircuit(int[] gas, int[] cost) {
        if(gas == null || cost == null || gas.length == 0 || cost.length == 0 || gas.length != cost.length) {
            return -1;
        }
        int total = 0, sum = 0, index = 0;
        for(int i = 0; i < gas.length; i++) {
            sum += gas[i] - cost[i];
            total += gas[i] - cost[i];
            if(sum < 0) {
                index = i + 1;
                sum = 0;
            }
        }
        return total < 0 ? -1 : index;
    }
}