CareerCup

for(each number i from the given digits)
{
printf(binaryToGray( i));

}
unsigned int binaryToGray(unsigned int num)
{
return (num >> 1) ^ num;
}

nth gray code = n ^ floor(n/2)

rest is simple

void grey_code(int n)
{
r=pow(2,n);
int a[n];
for(i=0;i<r;i++)
{
k=i;
for(j=n-1;j>=0;j--,k/=2)
a[j]=k%2;
k=0;
for(j=0;j<n;j++)
{
if(k==0)
{
if(a[j]==1)
k++;
printf("%d",a[j]);
}
else if(a[j]==a[j-1])
printf("0");
else
printf("1");
}
printf("\n");
}
}

n represent the bit number.
Code tested in Java.
Output in String. Could use out.print to reduce memory consumption if need.
Run-time O(n*2^n) to output n*2^n char. Memory O(n) extra.

public static void run(int n) {
    String gc="";//gray code output string
    Boolean flip;//determine gray code reflection
    int cur;//temp value to store baise
    int[] index = new int[n];//reflection length, used to determine if the number of certain index took a reflection or not
    for (int i = 0; i < n; i++) {//init index
        index[i] = (int) Math.pow(2, i);
    }
    for(int i=0; i<Math.pow(2,n);i++){//output gray code one by one
        flip=false; cur=0;
        for (int j=n-1;j>=0;j--){
            if(i>=index[j]+cur){
                if(flip) gc+="0";else {gc+="1";flip=true;}
                cur+=index[j];
            }else{
                if(flip) {gc+="1";flip=false;}else gc+="0";
            }
        }
        gc+=" ";
    }
}

#include<stdio.h>
#include<malloc.h>
#include<math.h>
#include <string.h>     /* strcat */
#include <stdlib.h>     /* strtol */

int *array,counter = 0;

void byte_to_binary(int x,int n)
{
    static char b[9];
    b[0] = '\0';

    int z;
    for (z = 128; z > 0; z >>= 1)
    {
        strcat(b, ((x & z) == z) ? "1" : "0");
    }
    int i = 8-n;
	while(i<8){
    	printf("%c",b[i]);
    	i++;
    }
}

int greycode(int n )
{
	int k,i;
	array[counter++]=0;
	array[counter++]=1;
	for(i=1 ; i < n; i++){
		k = counter -1;
		while(k>=0){
			array[counter++] = array[k--] | 1<<i;
		}
	}
	
} 
main()
{
	int n,i;
	printf("\nEnter n\n");
	scanf("%d",&n);
	array = (int*)malloc(pow(2,n)*sizeof(int));
	greycode(n);
	printf("\n------------------------greycode------------------------------\n");
	for(i=0;i<counter;i++){
		byte_to_binary(array[i],n);
		printf("\n");
	}
}

void CreateGrayCode(string str[], int arrayLen, int currLen, int length)
{
	if(currLen == length)
	{
		for(int i=0;i<arrayLen;i++) cout<<str[i]<<endl;
		return;
	}
	string *newstrArray = new string [arrayLen*2];
	for(int i= 0;i<arrayLen;i++)
	{
		string temp1 = "0";
		temp1.append(str[i]);
		string temp2 = "1";
		temp2.append(str[i]); 
		newstrArray[i] = temp1;
		newstrArray[2*arrayLen-i-1] = temp2;  

	}
		CreateGrayCode(newstrArray, arrayLen*2, currLen+1, length);
		return;

}
int main()
{
	int m = 4; //Lets  default it to 4 bits.
	string strArray[] = {"0", "1"};
	CreateGrayCode(strArray,2,1,m);
	return 0;
}

the total number of grey codes of n is 1 << n
nth codes add 1 << (n - 1) codes to the n-1 th codes
let i loop from 1 to n and update those 1 << (n-1) by adding radix, which is 1 << (n-1), to the corresponding codes,

no recursion needed

public int[] geryCodes(int n)
	{
		int[] a = new int[1 << n];
		int k = 1;
		int p = 0;
		int r = 1;
		for(int i = 1; i <= n; i++) {
			for(int j = 1; j <= 1 <<(i - 1); j++) {
				a[k] = r + a[p];
				p--;
				k++;
			}
			p = k -1;
			r <<= 1;
		}
		return a;
	}

guys u can try below code. Its based on recursion approach...
code is self explanatory...

public void greyCodeGen(String str,int i,int MAX){

if(i==MAX){
System.out.println(str);
}else{
greyCodeGen(str+'0',i+1,MAX);
greyCodeGen(str+'1',i+1,MAX);
}
}
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int x;
while((x=scan.nextInt())>0){
greyCodeGen("",0,x);
}
}

nth gray code sequence =n-1sequnce+ reverse n-1 sequence and add 2^(n-1)
f(2)= ( 00 ,01,11,10)
f(3) ={reverse= (10,11,01,00)and then add 1 in front
={000,001,011,010,110,111,101,100}

There is a direct formula for this nth grey code is n xor floor(n/2)

import java.util.ArrayList;

public class GrayCode {

	public static ArrayList<Integer> grayCode(int n) {
		ArrayList<Integer> list = new ArrayList<Integer>();
		if (n == 0) {
			list.add(0);
			return list;
		} else {
			ArrayList<Integer> prev = grayCode(n - 1);
			list.addAll(prev);
			for (int i = prev.size() - 1; i >= 0; i--) {
				list.add(prev.get(i) + (int) Math.pow(2.0, n - 1));

			}
			return list;
		}

	}

	public static void main(String[] args) {
		ArrayList<Integer> result = grayCode(2);
		for (int i : result) {
			System.out.print(i + " ");
		}
		// you could generate to binary form
		for (int i : result) {
			System.out.print(Integer.toBinaryString(i) + " ");
		}
	}

}

import java.util.Scanner;
class grayCode
{
static int matr[][]=new int[20][20];
static int number,row,column;


public static void main(String args[]){
Scanner sc = new Scanner(System.in);
System.out.println("Enter no.");
number=sc.nextInt();

row=(int)Math.pow(2,number);
column=number;

for(int i=0;i<number;i++)
{
fillCol(i);
}
for(int ii=0;ii<row;ii++)
{
for(int jj=0;jj<column;jj++)
System.out.print(matr[ii][jj]);
System.out.println();
}
}

static void fillCol(int colno)
{
int j=0;
int i=0,flag=1;
int ncoll=number-colno;
int packet=(int)Math.pow(2,ncoll);
int zero=(int)Math.pow(2,ncoll-1);
//System.out.println("p="+packet+" z="+zero+ "col no="+colno );
for(j=0;j<zero;j++)
{
matr[j][colno]=0;
}
for(j=zero;j<row;j++)
{
if(packet==0)
{ packet=(int)Math.pow(2,ncoll);
if(flag==1)
flag=0;
else if(flag==0)
flag=1;
}
matr[j][colno]=flag;
packet--;
}

}
}

please can anyone tell me the code for checking if two strings are grey code or not?