Generate unique four digit number

[Bhadrak]

Hi friends,

I want to generate four digit unique number which i can give it to my employees everyday because everyday whenever an employee comes in the office he gets a new four digit PIN number which he has to use it while accessing any computer.So is there any code where i can generate four digit unique number each and every time.

[Zecho]

Use the following code for creating four digit unique number.

#include <stdio.h>
#include <stdlib.h>
#include <time.h>                              

int main(void)

{
int i, n=4, p, q, r,s;    

p = rand() % 10;   /* First digit can be any within the set */
q = rand() % 9;    /* Second digit can be any except one (p) */

/* If p == q, it's safe to add 1 to q, because q's initial value is 0-8 */
if( q == p )
  q++;

r = rand() % 8;    /* Third digit can be any except two (a or q) */

if( ( r == p ) || ( r == q ) )
{
  r++;
  if( ( r == p ) || ( r == q ) )
    r++;
}

/* More of the same for s. Check against p, q, and r for uniqueness */
s = rand() % 7;    /* Fourth digit can be any except three (p, q, or r) */
if( ( s == p ) || ( s == q ) || ( s == r ) )
{
  s++;
  if( ( s == p ) || ( s == q ) || ( s == r ) )
  {
    s++;
    if( ( s == p ) || ( s == q ) || ( s == r ) )
      s++;
  }
}

[MindSpace]

Use the following code to create four digit number in Java

public class RandomNumber {

public static void main(String[] args) {

// Take a random number who's range will be
// 0 - 1 and multiply it by 8847. This
// will give you an double and then you
// can cast it to an int.
int value = (int)(Math.random() * 8847);

System.out.println(value);
}
}

[SunilWagh]

Use the following code for creating 10 digit unique number on the basis of dates. It is unique in seconds level not design for milliseconds.
this program will create unique numbers upto 52 years, reset it with changing 'adder' value.

Author : Sunil Wagh (SCJP, SCWCD, OCP , IBM Maximo 7 Certified)
--------------------------------------------------------------------------
import java.text.DecimalFormat;
import java.util.Calendar;

public class Demo2 {
// truncate four digit to two digit 2010=>10
public static int retval(int y){
String yrs=""+y;
yrs=yrs.substring(1);
y = Integer.parseInt(yrs) ;
return y;
}
// Create 10 Digit Unique number
public void test(){
int adder = 55;//Number Start from year 2010, change 64 to start from 2001
Calendar cal = Calendar.getInstance();
int year = cal.get(Calendar.YEAR);
int doy = cal.get(Calendar.DAY_OF_YEAR);
int hr = cal.get(Calendar.HOUR_OF_DAY);
int mi = cal.get(Calendar.MINUTE);
int ss = cal.get(Calendar.SECOND);
int yr = adder+retval(year);
char c=(char)yr;
DecimalFormat df = new DecimalFormat("000");
System.out.println("Unique Num: " + c + df.format(doy) + hr + mi + ss);
}

public static void main(String a[]){
Demo2 d = new Demo2();
d.test();
}
}
-------------------------------------------------------------------------
Output : Unique Num: A23117587
------------------------------------------------------------------------