Scala control flow Program: Find a factorial with a while loop

Last update on February 06 2025 12:40:55 (UTC/GMT +8 hours)

Write a Scala program to find the factorial of a given number using a while loop.

Pre-Knowledge (Before you start!)

• Basic Scala Syntax: Familiarity with writing and running Scala programs.
• Variables in Scala: Knowledge of declaring and initializing variables using var for mutable values.
• While Loops: Understanding how to use while loops for repetitive tasks.
• Arithmetic Operations: Ability to perform multiplication and decrement operations.
• String Interpolation: Awareness of embedding variables within strings using s"string ${variable}".
• Printing Output: Familiarity with the println() function to display output on the screen.

Hints (Try before looking at the solution!)

• Define the Main Object: Create an object with a main method, which serves as the entry point of the program.
• Initialize Variables: Declare a variable to store the number for which you want to calculate the factorial. Initialize another variable to store the factorial result, starting with 1.
• Use a While Loop: Use a while loop to iterate from the given number down to 1. Multiply the current factorial value with the loop variable in each iteration.
• Decrement the Counter: Decrease the loop variable by 1 in each iteration to move toward the base case.
• Display the Output: Use println() to print the calculated factorial in a readable format, including the number in the output message.
• Test with Different Numbers: Change the input number to verify the program works for various cases, including edge cases like 0 or large numbers.
• Common Errors to Avoid:
  • Forgetting to initialize the factorial variable as 1, leading to incorrect results.
  • Misplacing the decrement logic, causing infinite loops or incorrect calculations.
  • Not handling edge cases like 0, which should return 1 as the factorial of 0 is defined as 1.

Sample Solution:

Scala Code:

object FactorialCalculator {
  def main(args: Array[String]): Unit = {
    val number: Int = 4 // Number for which you want to find the factorial

    var factorial: Long = 1 // Initialize the factorial variable as 1
    var i: Int = number

    while (i > 0) {
      factorial *= i
      i -= 1
    }

    println(s"The factorial of $number is: $factorial")
  }
}

Sample Output:

The factorial of 4 is: 24

Explanation:

In the above exercise -

• First we define a variable "number" and assign it a value (5 in this case) for which we want to find the factorial. We initialize a variable factorial as 1 since the factorial of 0 is defined as 1. We also initialize a variable i with the value of "number".
• Inside the while loop, we multiply the current factorial value with i and store the result back in factorial. Then, we decrement the value of i by 1.
• The loop continues until i becomes 0. When the loop finishes, we print the result using println, which displays the factorial.

Scala Code Editor :

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