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.

Reference: http://blog.csdn.net/lbyxiafei/article/details/12183461

Method: like largest sum in a array

public class Solution {
    public int canCompleteCircuit(int[] gas, int[] cost) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        int total = 0, sum = 0;
        int index = -1; //start position initialized to -1!
        for(int i = 0; i < gas.length; i++){
            sum += gas[i] - cost[i];
            total += gas[i] - cost[i];
            if(sum < 0){
                index = i;
                sum = 0;
            }
        }
        
        return total >= 0 ? index+1:-1;  // index+1, not index
        
    }
}