Question

I am trying to develop code for SPOJ factorial problem number 11. The following is my code

import java.math.*; 
import java.io.*;
public class Problem11 {

/**
 * Count the number of zeroes at the end of 
 * the factorial value of a number.
 */
public static void main(String[] args) throws IOException
{
 BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
 int numOfInputs=0;
 numOfInputs=Integer.parseInt(br.readLine());
 BigInteger nextNum[]=new BigInteger[numOfInputs];
 BigInteger factValue[]=new BigInteger[numOfInputs];

 //Get all the numbers to be computed
 for(int count=0;count<numOfInputs;count++)
 {
    nextNum[count]=new BigInteger(br.readLine());
 }

 //Obtain the factorial value for each number
 for(int count=0;count<numOfInputs;count++)
 {
     factValue[count]=getFact(nextNum[count]);
 }

 //Obtain the number of trailing zeroes
 for(int count=0;count<numOfInputs;count++)
 {
     //System.out.println(factValue[count]);
     System.out.println(getZeroes(factValue[count]));

 }
}


public static String getZeroes(BigInteger num) 
 {
    int numOfZeroes=0;
    while(num.remainder(BigInteger.TEN).equals(BigInteger.ZERO))
    {
        num=num.divide(BigInteger.TEN);
        numOfZeroes++;
    }
    return String.valueOf(numOfZeroes);
 }



public static BigInteger getFact(BigInteger num) 
{
    BigInteger factorial=BigInteger.ONE;    
    if(num.equals(0))
    {
      return (BigInteger.valueOf(1));
    }
    else
    {
        int count=1;
        while((BigInteger.valueOf(count).compareTo(num))<=0)        
        {               
            factorial=factorial.multiply(BigInteger.valueOf(count));
            count++;
        }
    }

    return factorial;

}

}

The code works fine for numbers up to 5 digits with small delay and for the last number
8735373 it is taking too much time, if I submit my solution, the judge shows compilation error.. I am unable to figure out whats the error. Please have a look at my code and help me to trace the problem.

Answer 1

You might look at this method for finding the number of trailing zeros in n!.

import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int count = in.nextInt();
        for (int i = 0; i < count; i++) {
            int n = in.nextInt();
            int result = 0;
            for (int d = 5; d <= n; d *= 5) {
                result += n / d;
            }
            System.out.println(result);
        }
    }
}