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.

思路与求最大和的连续子序列十分相似。

Runtime: 1 ms beats 7.32% of javasubmissions

	public int canCompleteCircuit(int[] gas, int[] cost) {
		int tank = 0, total = 0, sub, start = 0;
		for (int i = 0; i < gas.length; i++) {
			sub = gas[i] - cost[i];//本次多余油量
			tank += sub;//油箱剩余油量
			if (tank < 0) {
				start = i + 1;
				tank = 0;
			}
			total += sub;
		}
		return total >= 0 ? start : -1;
	}