leetcode 134. 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. 明らかに、起点はgas-costがゼロより大きいところから始まり、このような点が連続している場合は、最初のような点だけを選択します.

class Solution {
public:
	int canCompleteCircuit(vector<int>& gas, vector<int>& cost) {
		if (gas.size() == 1)
		{
			if (gas[0] >= cost[0])
				return 0;
			else
				return -1;
		}
		vector<int>starter;
		int k = 0;
		while (k < gas.size())
		{
			if (gas[k] - cost[k] > 0)
			{
				int kk = k;
				starter.push_back(k);
				while (kk < gas.size() && gas[kk] - cost[kk] >= 0)
					kk++;
				k = kk;
			}
			k++;
		}
		for (int i = 0; i < starter.size(); i++)
		{
			int rem = 0;
			while (rem >= 0)
			{
				rem = gas[starter[i]] - cost[starter[i]];
				int kk = starter[i];
				int cnt = 1;
				while (rem >= 0)
				{
					kk++;
					if (kk == gas.size())
						kk = 0;
					rem += gas[kk] - cost[kk];
					cnt++;
					if (cnt == gas.size() && rem >= 0)
						return starter[i];
				}
			}
		}
		return -1;
	}
};

accept