leetcode 139: Gas Station

Gas Station

Total Accepted: 12612
Total Submissions: 51726
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 class Solution {
public int canCompleteCircuit(int[] gas, int[] cost) {
if(gas==null || cost==null || gas.length==0 || cost.length==0 || gas.length != cost.length) return -1;

int sum = 0;
int start = 0;
int totalGas = 0;
int totalCost = 0;
for(int i=0; i<gas.length; i++)  {
sum += gas[i] - cost[i];
totalGas += gas[i];
totalCost += cost[i];
if(sum<0) {
sum = 0;
start = i+1;
}
}

return totalGas>=totalCost ? start : -1;

}
}