CODEWITHSUNDEEP
java
Jason arora
Jason arora

Reputation: 550

How to find Number of trailing zeroes of number N

Given a number n, find out the number of zeroes at the end of decimal representation of n!

Input:

First line of input will contain T = number of test cases. Next T lines will each have one number n where 1<=n<=10^9. Find out number of trailing zeroes (zeroes at the end) in factorial of this number n.

Output:

There should be one line for each test case printing the number of trailing zeroes in factorial of the given number.

Sample Input

4

6

12

18

25

Sample Output

1

2

3

6

MyOutput

2

6

1

... //this indicates that the condition of entering input is not terminated and no output is produced.

MyApproach:

To calculate trailing zeros.I checked the number of 5 because if 5 is there 2 would definately be there which will make a zero at the end. So,I wrote the following code and also haven't checked the numbers are less than or equal to 4.

Below is my code:

 public static void zerosCount()
 {
  Scanner sc=new Scanner(System.in);

   int T=sc.nextInt();
   for(int i=0;i<T;i++)
   {
     int count5=0;
     int p=sc.nextInt();
      while(p>=1)
        {
          int n=p;
          while(n>=5)
           {
              if(n%5==0)
              {
                  count5++;
                  n=n/5;
              }
           }
         p--;
        }
       System.out.println(count5);
   }
         sc.close();
}

Why I am not able to get the correct output:

Can anyone guide me why?

Upvotes: 1

Views: 256

Answers (2)

Jason arora
Jason arora

Reputation: 550

This is how I solved the problem with the help of Narendra and radoh

I counted the no of 5 of whatever the input comes and check the number till it is greater than or equal to 5. Took the sum if a number has more than one zero or I say more than 1 5.

Upvotes: 0

Narendra Jaggi
Narendra Jaggi

Reputation: 1338

The approach mentioned by @radoh is incomplete and will result in wrong answer for number like 100 which has 24 zeros but n/5 will get only 20.
the number of zeros depends on 5s. so if the
N = 5 then divide it by 5 which gives 1
N= 10 then divide it by 5 gives 2
N=25 then divide it by 5 and 25
N = 50 then divide it by 5 and 25 will give you 12
N = 100 then divide it by 5 25 will give you 24
so the bottom line is after every divide , do the multiply the 5 with 5 and if the result of multiplication is less than the equals to N then divide the N with result and add the zeros counter variable.

Upvotes: 2

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