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;
    }
};