求这个程序的算法！！在线等，急！！！！！！

public class Test {



  public static final String OPERATORS = " +-*";



  public static final int STEP_LIMIT = 12;



  public static final BigDecimal VALUE = BigDecimal.valueOf(2);



  public static void main(String[] args) throws Exception {

    int[] operators = new int[STEP_LIMIT];

    Scanner scanner = new Scanner(System.in);

    System.out.println("Please input A:");

    String aStr = scanner.next();

    BigDecimal a = new BigDecimal(aStr);

    System.out.println("Please input B:");

    String bStr = scanner.next();

    BigDecimal b = new BigDecimal(bStr);

    if (find(a, b, operators, 0)) {

      System.out.println(toExpression(a, b, operators));

    } else {

      System.out.println("Oops!");

    }

  }



  public static boolean find(BigDecimal from,

                             BigDecimal to,

                             int[] operators,

                             int step) throws Exception {

    if (step >= STEP_LIMIT) {

      return false;

    }

    if (from.compareTo(to) == 0) {

      return true;

    }

    for (int operator = 1; operator < OPERATORS.length(); operator++) {

      operators[step] = operator;

      if (find(newValue(from, operator), to, operators, step + 1)) {

        return true;

      }

    }

    operators[step] = 0;

    return false;

  }



  public static BigDecimal newValue(BigDecimal from, int operator) {

    switch (operator) {

      case 1:

        return from.add(VALUE);

      case 2:

        return from.subtract(VALUE);

      case 3:

        return from.multiply(VALUE);

      default:

        throw new RuntimeException();

    }

  }



  public static String toExpression(BigDecimal a, BigDecimal b, int[] operators) {

    StringBuilder buff = new StringBuilder(30).append(a);

    for (int i = 0; i < operators.length && operators[i] != 0; i++) {

      int operator = operators[i];

      buff.append(OPERATORS.charAt(operator)).append(VALUE);

    }

    return buff.append("=").append(b).toString();

  }

}