[RESOLVED] different answer

Hello

i was tring to figure out what the result of factorial for 21 using the following code.

java code

Code:

---

import java.io.*;
/**
 *
 * @author 
 */
public class mywelcome {
  public static void main (String[] args) throws IOException
  {
    BufferedReader userin = new BufferedReader
        (new InputStreamReader(System.in));
    String inputData;
    long    N, fact = 1;

    System.out.println( "Enter N:" );
    inputData = userin.readLine();
    N        = Integer.parseInt( inputData );

    if ( N >= 0 )
    {
      while ( N > 1 )   
      {
        fact = fact * N;
        N    = N - 1;
      }
      System.out.println( "factorial is " + fact );
    }
    else
    {
      System.out.println("N must be zero or greater");
    }
  }
}

---

when i use the code in the netbeans environment, i get the answer -4249290049419214848
but the following link states the answer should be 51090942171709440000

http://chortle.ccsu.edu/CS151/Notes/...r+greater&N=20

can you guys tell me why the difference?

I don't agree with what how you're doing it. Simply use a for loop:

Code:

---

long total = 1;
for (int index=21; index >=1; --index)
{
  total *=index;
}

---

Something along those lines... You can use recursion, but I'd prefer this method.

That's JavaScript, it's totally different than java besides "51090942171709440000" is very big to contain in a "long" variable,
try this:

Code:

---

import java.io.* ;

/**
 *
 * @author  Moyeen
 */
public class My
{
  public static void main (String[] args) throws IOException {
    BufferedReader userin = new BufferedReader(new InputStreamReader(System.in)) ;
    String inputData ;
    int N;
    double fact = 1 ;

    System.out.println("Enter N:") ;
    inputData = userin.readLine() ;
    N = Integer.parseInt(inputData) ;

    if (N >= 0) {
      while (N > 1) {
        fact = fact * N ;
        N-- ;
      }
      System.out.println("factorial is " + fact) ;
    }
    else {
      System.out.println("N must be zero or greater") ;
    }
  }
}

---

thanks for the replies

i have just started on java, and am going through this tutorial on central conneticut state university's web tutorial on java

Good, welcome to java :D
if you are done, please mark the thread resolved

done. thanks again

http://www.vbforums.com/images/ieimages/2006/04/1.gif this is not how you mark a thread resolved!
Click on "Thread Tools" and select "Mark Thread Resolved"

double is potentially inaccurate. Use java.math.BigInteger instead. Note that you have to use the class's member functions instead of normal mathematical operators, though.

done :)