CODE 131: 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.

public int canCompleteCircuit(int[] gas, int[] cost) {// IMPORTANT: Please reset any member data you declared, as// the same Solution instance will be reused for each test case.if (null == gas || gas.length <= 0) {return -1;}for (int i = 0; i < gas.length; i++) {gas[i] -= cost[i];}int i = 0;int j = 0;int sum = 0;for (; i < gas.length; i++) {if (gas[i] < 0) {continue;}sum = gas[i];j = (i + 1) % gas.length;while (sum >= 0 && j != i) {sum += gas[j];j = (j + 1) % gas.length;}if (j == i) {break;}if (j > i) {i = j;}}if (i < gas.length && j == i && sum >= 0) {return i;} else {return -1;}}