LeetCode - Gas Station

Gas Station

//
public int canCompleteCircuit(int[] gas, int[] cost) {
        if(gas == null || gas.length == 0 || cost == null || cost.length == 0) return -1;
        int total = 0, local = 0, index = 0;
        for(int i=0; i<gas.length; i++){
            total += gas[i] - cost[i];
            local += gas[i] - cost[i];
            if(local < 0){
                index = i + 1; // don't write index = i;
                local = 0;
            }
        }
        if(total < 0) return -1;
        return index;
    }
    
//
public int canCompleteCircuit(int[] gas, int[] cost) {
        int len = gas.length, sum=0, total=0, idx=-1;
        for(int i=0; i<len; i++){
            sum += gas[i] - cost[i];
            total += gas[i] - cost[i];
            if(sum<0){
                sum=0;
                idx=i;
            }
        }
        return total>=0 ? idx+1 : -1;
    }