gas station leetcode

class Solution {public:    int canCompleteCircuit(vector<int> &gas, vector<int> &cost) {        int sum=0,total=0,i,start=0;        for(i=0;i<gas.size();i++)        {            sum=sum+gas[i]-cost[i];            total=total+gas[i]-cost[i];            if(sum<0)            {                sum=0;                start=(i+1)%gas.size();            }        }        if(total<0)            return -1;        else           return start;    }};

这题用笨办法会超时，看了http://blog.csdn.net/jellyyin/article/details/12245429，才知道好办法