The Moronic Cowmpouter

 Inexperienced in the digital arts, the cows tried to build a calculating engine (yes, it's a cowmpouter) using binary numbers (base 2) but instead built one based on base negative 2! They were quite pleased since numbers expressed in base -2 do not have a sign bit.

You know number bases have place values that start at 1 (base to the 0 power) and proceed right-to-left to base^1, base^2, and so on. In base -2, the place values are 1, -2, 4, -8, 16, -32, ... (reading from right to left). Thus, counting from 1 goes like this: 1, 110, 111, 100, 101, 11010, 11011, 11000, 11001, and so on.

Eerily, negative numbers are also represented with 1's and 0's but no sign. Consider counting from -1 downward: 11, 10, 1101, 1100, 1111, and so on.

Please help the cows convert ordinary decimal integers (range -2,000,000,000 .. 2,000,000,000) to their counterpart representation in base -2.
Input

A single integer to be converted to base -2
Output

A single integer with no leading zeroes that is the input integer converted to base -2. The value 0 is expressed as 0, with exactly one 0. 

Example
Input:
-13

Output:
110111

https://www.spoj.pl/problems/NEG2/

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class TheMoronicCowmpouter 
{
   public static void main( String args[] ) throws Exception
   {
      BufferedReader br = new BufferedReader( new InputStreamReader( System.in ) );
  
      int numero = Integer.parseInt( br.readLine() );
   
      boolean redondeoAbajo = true;
      int prueba = numero;
  
      if( numero < 0 )
      {
         prueba = -prueba;
         redondeoAbajo = false;
      }
  
      //Buffer temporal donde almacenaremos la salida
      char[] salida = new char[ 35 ];
      int tamanio = 35;
   
      if( numero == 0 )
         System.out.println( "0" );
  
      else
      {
         /*
         * Nos basamos en el algoritmo presentado en 
         * http://en.wikipedia.org/wiki/Negative_base, realizamos 
         * una ligera modificacion para que solo tengamos que
         * trabajar con numeros enteros positivos.
         * 
         * La modificacion consiste en ir redondeando alternadamente
         * hacia arriba y hacia abajo, luego de realizar cada division.
         */
         while( prueba > 0 )
         {
            // Verificamos si el numero actual es par
            if( ( prueba & 1 ) == 0 )
               salida[ -- tamanio ] = '0';
            else
               salida[ -- tamanio ] = '1';
    
            if( redondeoAbajo )
               prueba = prueba >> 1;
            else
               prueba = ( prueba + 1 ) >> 1;
    
            redondeoAbajo = !redondeoAbajo;
         }
   
         System.out.println( new String( salida, tamanio, 35 - tamanio ) );
      }
   }
}