CareerCup

import java.util.Calendar;
import java.util.Scanner;

class RandomNumber {
	static long seed = 0;

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = Integer.parseInt(scan.next());
		long r = randomn(n);
		scan.close();
		System.out.println(r);
	}

	static private long randomn(int n) {
		Calendar calendar = Calendar.getInstance();
		long reandomnum = 0;
		long m = calendar.getTimeInMillis() + calendar.get(Calendar.SECOND)
				+ (60 * calendar.get(Calendar.MINUTE))
				+ (3600 * calendar.get(Calendar.HOUR));
		if (seed == 0) {
			seed = m;
		}
		reandomnum = (m + seed) % n;
		return reandomnum;
	}
}

Is this on the skills round or or site interview?

!offtopic | Anon

no response yet! someone please answer this question. the question is really nice.

anybody out there

this question even for n=7 has been asked many times but never a satisfactory solution was provided either by using existing random function of values 0 and 1 or by anyother means...I've never found any solution which generates n random numbers with equal probability but I am curious to know d solution as well....i think loler can answer this one better..

LOLer wr r u? we're eagerly waiting for your answer.

Unrelated but nice one:
This is an optimized way of Sieve of Erato used for finding primes, check it out:
http://en.wikipedia.org/wiki/Sieve_of_Atkin

wtf.....

I think I have the solution. Please tell me if its right or wrong.
To create a random number between 0 and n. Divide the whole range by n. So the question now becomes generating a random number from 0 to 1.
check for n=0, no sense generating numbers from 0 to zero so throw an logical exception.
We need something that is random and keep changing without our intervention.So I opted for the system clock.
DateTime dt = DateTime.Now;
seconds = dt.Second;
// update time if seconds change
if(seconds != dt.Second) {
seconds = dt.Second;
try
{
secondsNum = Convert.ToInt32(seconds);
}
catch (FormatException e)
{
Console.WriteLine("Input string is not a sequence of digits.");
}

x = (1/ secondsNum*n)]
for any n> 0 , mutliply n with [1 - 1/x] could solve our problem.
but if n is very small and tending to zero then 1-1/x would be a negative number.
So I have made
y = 1/(1+x).
now [1-1/y] should gives us a randon number

I made a mistake in the above solution just a typo. x = secondsNum*n
and random number is [1-1/y]n.

solution looks fine....but `baba sainath` wouldnt't something like (secondsNum%n) be ok as well ? As in I am fine till the secondsNum thing...but the later part to it looks a bit complicated, even as I said before...seems to be working fine . What say?

@Baba je :)

can u explain me about this y=1/(1+x) and 1-1/y thing i tried solving it essentially 1-1/y equal to x itself which will be always less then n can u please explain by taking some example values say n=5 and take any random second value

can we just malloc a piece of mem, and peek what's in there? Is that random enough?

how about this

void printRandom(int n)
DateTime dt = DateTime.Now; 
seconds = dt.Second+60*dt.Minute+3600*dt.Hour;
random=second%n;
cout << random;

class Program
{
static long seed = 0;
static void Main(string[] args)
{
int n = Convert.ToInt32(Console.ReadLine());
int r = randomn(n);
Console.WriteLine(r.ToString());
Console.ReadLine();
}
static private int randomn(int n)
{
DateTime dt = DateTime.Now;
int reandomnum = 0;
long m = dt.Millisecond + dt.Second + 60 * dt.Minute + 3600 * dt.Hour;
if(seed == 0)
{
seed = m;
}
reandomnum = Convert.ToInt32((m + seed) % n);
return reandomnum;
}
}

public static void main(String[] args) {
Calendar calendar = new GregorianCalendar();
long second =(calendar.getTimeInMillis());
System.out.print(second);
Scanner scan = new Scanner(System.in);
String userInp;
System.out.print("Enter the input");
userInp = scan.next();
long n = Integer.parseInt(userInp);
second=second%10;
System.out.println("The random number is "+second);


}

use LCG(linear congruential Generators (ax+b mod n)

Sample code --> stackoverflow.com/questions/648976/random-number-generator

package epic.java;
import java.util.Date;
import java.util.Scanner;
public class GenerateRandomNumber {
	public static void main(String[] args){
		
		Scanner scan=new Scanner(System.in);
		long num=1;
		while(num!=0){
		System.out.println("Enter your num: \n");
		num=scan.nextLong();
		if(num>0)
		 System.out.println("Random Number: "+random(num));	
	}		
		scan.close();
		
	}
	
	public static long random(long num){
		Date date=new Date();
		long timeStamp=date.getTime();
		long ran=timeStamp%num;		
		return ran;
	}
	
}

{}