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.
Solution:
1. public class Solution {
2. public int canCompleteCircuit(int[] gas, int[] cost) {
3. int pos = -1;
4. int curr = 0, total = 0;
5. 6. for (int i = 0; i < gas.length; i++) {
7. int diff = gas[i] - cost[i];
8. 9. curr += diff;
10. total += diff;
11. 12. if (curr < 0) {
13. curr = 0;
14. pos = i;
15. }
16. }
17. 18. if (total >= 0) {
19. return pos + 1;
20. }
21. 22. return -1;
23. }
24. }