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;
}