LeetCode OJ - 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.

分析：DP学艺不精，用了发现不对，因为找的子问题没有重复子问题，故仅仅是递归。

采用两层循环，时间复杂度为O(n*n)，估计不满足要求。

class Solution {public:    int canCompleteCircuit(vector<int> &gas, vector<int> &cost) {        // Note: The Solution object is instantiated only once and is reused by each test case.        int sum=0;        int total=0;        int start=0;        for(int i=0;i<gas.size();i++)        {            sum+=gas[i]-cost[i];            total+=gas[i]-cost[i];            if(sum < 0)            {                start=(i+1)%gas.size(); sum=0;            }        }                if(total <0)            return -1;        else            return start;    }};