Gas Station
Source
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.
Example
Given 4 gas stations with gas[i]=[1,1,3,1], and the
cost[i]=[2,2,1,1]. The starting gas station's index is 2.
Note
The solution is guaranteed to be unique.
Challenge
O(n) time and O(1) extra space
Java
public class Solution {
public int canCompleteCircuit(int[] gas, int[] cost) {
int start=0;
int sum=0;
int total=0;
for(int i=0; i<gas.length; i++){
sum += gas[i]-cost[i];
total += gas[i]-cost[i];
if(sum<0){
start=i+1;
sum=0;
}
}
if(total<0){
return -1;
}
return start;
}
}