Java: Compute the number of trailing zeros in a factorial

Last update on May 12 2025 13:12:37 (UTC/GMT +8 hours)

Trailing Zeros in Factorial

Write a Java program to compute the number of trailing zeros in a factorial.

Example
7! = 5040, therefore the output should be 1.

Pictorial Presentation:

Java Basic Exercises: Compute the number of trailing zeros in a factorial

Sample Solution:

Java Code:

import java.util.Scanner;

public class Example112 {
    public static void main(String[] arg) {
        Scanner in = new Scanner(System.in); // Create a Scanner object for user input
        System.out.print("Input a number: "); // Prompt the user to input a number
        int n = in.nextInt(); // Read and store the user's input as 'n'
        int n1 = n; // Create a copy of 'n' to preserve the original value
        long ctr = 0; // Initialize a variable 'ctr' to count trailing zeros

        while (n != 0) {
            ctr += n / 5; // Count the number of trailing zeros by dividing 'n' by 5 and accumulating the result
            n /= 5; // Reduce 'n' by dividing it by 5 for the next iteration
        }
        System.out.printf("Number of trailing zeros of the factorial %d is %d ", n1, ctr); // Print the result
        System.out.printf("\n"); // Print a new line
    }
}

Sample Output:

Input a number : 5040                                                  
Number of trailing zeros of the factorial 5040 is 1258

Flowchart:

Flowchart: Java exercises: Compute the number of trailing zeros in a factorial

For more Practice: Solve these Related Problems:

Modify the program to return the number of trailing ones instead.
Write a program to find the highest power of 2 in the factorial.
Modify the program to return the count of factors of 5 in the factorial.
Write a program to compute the factorial without storing large numbers.

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