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OPTIMIZING A SWIFT FUNCTION FOR CALCULATING THE DIGITAL ROOT

Mostafa Davoodi

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GoPenAI

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2 min read
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Apr 26, 2023

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As a software engineer, I often encounter various coding problems, and I’m
always looking for ways to optimize my code for efficiency and performance.
Recently, I came across an interesting problem that required calculating the
Digital Root of a given integer. In this post, I’ll share my journey of
optimizing the solution in Swift.


THE PROBLEM

The task is to write a function that takes a non-negative integer as input and
returns its Digital Root. The Digital Root is the iterative process of summing
the digits of a number until a single-digit number is obtained.


INITIAL IMPLEMENTATION

Here’s the initial implementation in Swift:

func addDigits(_ num: Int) -> Int {
    var num = num
    while num > 9 { 
        num = Array(String(num)).map{ Int(String($0)) ?? 0 }.reduce(0,+)
    }
    return num
}

This implementation works, but it’s not very efficient as it creates new arrays
and strings in each iteration. This increases memory usage and runtime
complexity.


OPTIMIZED IMPLEMENTATION

To optimize the function, we can eliminate the use of arrays and strings by
using basic arithmetic operations:

func addDigits(_ num: Int) -> Int {
    var num = num
    while num > 9 {
        var sum = 0
        while num > 0 {
            sum += num % 10
            num /= 10
        }
        num = sum
    }
    return num
}

This version is more efficient as it avoids creating new arrays and strings in
each iteration.


FURTHER OPTIMIZATION USING DIGITAL ROOT FORMULA

After some research, I discovered that there’s an even more efficient solution
using the mathematical properties of numbers. The Digital Root can be calculated
using the following formula:

Digital Root = 1 + (num — 1) % 9

Using this formula, we can eliminate the need for loops and significantly
improve runtime:

func addDigits(_ num: Int) -> Int {
    if num == 0 {
        return 0
    } else {
        return 1 + (num - 1) % 9
    }
}

This version is highly efficient as it removes the need for any loops and
directly calculates the result using the given formula.


CONCLUSION

Optimizing code is an essential skill for every software engineer. By analyzing
the problem, understanding the underlying mathematical properties, and using
efficient algorithms, we can significantly improve the performance of our code.
In this case, we optimized the Digital Root calculation in Swift using the
Digital Root formula. This not only reduced memory usage but also resulted in a
much faster solution.

PS: This post description is generated by ChatGPT. I passed my 3 Swift
implementations for the Digital Root problem and asked it to generate a Medium
post based on them. The AI provided a comprehensive explanation of each
implementation, showing the optimization process and improvements made along the
way.





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Algorithms
Software Engineering
Problem Solving
ChatGPT


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WRITTEN BY MOSTAFA DAVOODI

12 Followers
·Writer for

GoPenAI

Senior Software Engineer, https://www.linkedin.com/in/mostafa-davoodi/

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