CareerCup

class GasStation {

public static int canCompleteCircuit(int[] gas, int[] cost) {
if(gas == null || cost == null) return -1;

int total = 0;
int upToNow = 0;
int startPos = 0;
for(int i=0; i<gas.length; i++) {
int delta = gas[i] - cost[i];
if(upToNow >= 0) upToNow += delta;
else {
upToNow = delta;
startPos = i;
}
total += delta;
}

return total >= 0 ? startPos : -1;
}

public static void main(String[] args) {
int[] gas = {3,5,7};
int[] cost = {8,4,3};
System.out.println(canCompleteCircuit(gas, cost));
}
}

With smallest use of memory and O(n^2) .

public class StringCompress
{
    public static String compress(final String source)
    {
        String str = source;
        final StringBuilder sb = new StringBuilder();
        int i = 0;
        int max = 1;
        max = firstSubstringWithoutDuplication(source);
 
        String last = str.substring(i,i+max);
        int j=i+1;
        i = i+max; 
        int count = 1;
        boolean flag = true;
        String current = "";
        while (i < str.length())
        {
            if(i+max<=str.length())
               current = str.substring(i,i+max);
            else 
                current = str.substring(i);
            if (current.equals(last))
            {
                count++;
                i = i+max;
                flag = false;
            }
            else if(flag)
            {
                sb.append(count);
                sb.append(last.charAt(0));
                count = 1;
                max = firstSubstringWithoutDuplication(source.substring(j));
                if(j+max<=str.length())
                   last = str.substring(j,j+max);
                else
                   last = str.substring(j);
                i=j+max;
                j=j+1;
            }
            else
            {
                sb.append(count);
                sb.append(last);
                count = 1;
                max = firstSubstringWithoutDuplication(source.substring(i));
                last = str.substring(i,i+max);
                i=i+max;
 
            }
        }
        sb.append(count);
        sb.append(last);
        return sb.toString();
    }
 
    public static void main(final String[] args)
    {
       System.out.println(compress("aab"));
       System.out.println(compress("aasasatb"));
       System.out.println(compress("abcdbcdff"));
       System.out.println(compress("xyzabcdbcdff"));
    }
 
    public static int firstSubstringWithoutDuplication(String str) {
        int maxLength = 1;
 
        int checker = 0;
        for (int i = 0; i < str.length(); i++) {
            int val = str.charAt(i) - 'a';
            if ((checker & (1 << val)) > 0){ return i; }
            checker |= (1 << val);
        }
 
        return maxLength;
    }
}

Yes they can send emails simultaneously and machines having equal processing power.