/**
 * COMP 1711 (Fall 2005)
 *
 * Solution to Challenge Problem #2 (Binary Strings)
 * 
 * The method in this class converts binary strings into non-negative integers.
 * 
 * @author  Based on a solution by Geoffrey Bouchard 
 * @version Dec-08-2003
 */

public class Problem02
{
    // Behaviour is same as for problem description, except also returns -1
    // for a non-null empty String
    public static int toNonNegInt(String binNum)
    {
        if ((binNum == null) || (binNum.equals("")))
        {
            return -1;
        } // end if

        // Return -1 if any character in String is NOT '0' or '1'
        for (int i=0; i < binNum.length(); i++)
        {
            if ((binNum.charAt(i)!='0') && (binNum.charAt(i)!='1'))
            {
                return -1;
            } // end if
        } // end for
        
        int integer = 0;  // Holds the answer
        double exp = 0.0; // Needed for the power function.
        for (int i = binNum.length()-1; i >= 0; i--)
        {
            if (binNum.charAt(i) == '1')
            {
                integer += (int) Math.pow(2.0, exp);
            } // end if
            exp++;
        } //end for
        return integer;
    } // end toNonNegInt(String)

} // end class Problem02