import java.util.Random;

public class ECUtilities {

	public static int binary2gray(int n){
		// n has 32 bits: n(31), n(30),..., n(1), n(0)
		int result,br,bl;

		br = (n & 0x80000000) == 0? 0:1; // br: the most significant bit of n, it is n(31)
		// bl: is the second most significant bit of n, it is n(30)
		result = br;

		for(int i=0; i < 31; i++){
			n <<= 1;
			bl = (n & 0x80000000) == 0? 0:1;
			result <<= 1;
			result |= (br^bl);
			br = bl;
		}

		return result;
	}

	public static int gray2binary(int a){

		int lb = (a & 0x80000000) == 0? 0:1;
		int result = lb;

		for(int i=0; i < 31; i++){

			a <<= 1;
			lb = lb ^ ((a & 0x80000000) == 0? 0:1);
			result <<= 1;
			result |= lb;
		}

		return result;
	}

	public static String binaryString(int n,int size){
		// convert n to its binary equvalent in a String of length "size"
		// for example binaryString(3,4) returns "0011"
		// and binaryString(3,8) returns "00000011"

		if( size < 1 || size > 32 )
			System.err.println("error: bad argument for binaryString");

		String result = "";
		for(int i=0; i < size; i++){
			result = ((n & 1) == 0? 0:1) + result;
			n >>= 1;
		}
		return result;
	}

  public static void main(String[] args) {

  }
}