ZipInt

public class ZipInt {
  public static void main(String[] argv) {
    ZipInt zi = new ZipInt();
    System.out.println(zi.solution(12, 56));
    System.out.println(zi.solution(56, 12));
    System.out.println(zi.solution(12345, 678));
    System.out.println(zi.solution(123, 67890));
    System.out.println(zi.solution(10, 100));
    System.out.println(zi.solution(0, 0));
    System.out.println(zi.solution(2, 0));
    System.out.println(zi.solution(0, 2));
    System.out.println(zi.solution(100000000, 100000000));
  }

  public int solution(int A, int B) {
    long result = 0;

    int baseA = base(A);
    int baseB = base(B);

    while (baseA > 0 && baseB > 0) {
      result = result * 100 + (A/baseA) * 10 + (B/baseB);
      A %= baseA;
      B %= baseB;
      baseA /= 10;
      baseB /= 10;
    }

    while (baseA > 0) {
      result = result * 10 + A/baseA;
      A %= baseA;
      baseA /= 10;
    }

    while (baseB > 0) {
      result = result * 10 + B/baseB;
      B %= baseB;
      baseB /= 10;
    }

    return (result > 100000000) ? -1: (int)result;
  }

  public int base(int x) {
    int b = 1;
    while (10 * b <= x) {
      b *= 10;
    }
    return b;
  }
}