leetcode之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.

问题链接

cpp代码如下：

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