134. Gas Station java solutions

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.

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

参考思路：

http://www.cnblogs.com/felixfang/p/3814463.html