Chapter 1: Understanding the Problem

Today’s DevAdvent challenge focuses on the fascinating task of rearranging digits within a number. The goal is to transform a number into the largest possible value by rearranging its digits. This concept builds on previous challenges, including methods for finding minimum or maximum values in arrays and converting numbers to strings in JavaScript.

The task requires creating a function that accepts a non-negative integer and returns it with its digits sorted in descending order.

For instance:

• Input: 42145 → Output: 54421
• Input: 145263 → Output: 654321
• Input: 123456789 → Output: 987654321

Chapter 2: My Approach to the Solution

To tackle this challenge, I devised a solution consisting of five sequential steps:

1. Convert the number into a string to enable iteration.
2. Transform the string into an array of characters.
3. Sort the array in descending order based on numeric value.
4. Join the sorted characters back into a single string.
5. Convert the final string back into a number.

The complete function can be defined as follows:

export function descendingOrder(n: number): number {

const str: string = "" + n;

const strArray: string[] = [...str];

const sortedArray: string[] = strArray.sort((a, b) => +b - +a);

const arrayJoined: string = sortedArray.join("");

return +arrayJoined;

}

For a more concise implementation, I combined all steps into a single line:

export const descendingOrder = (x: number): number =>

+[...("" + x)].sort((a, b) => +b - +a).join("");

This streamlined version is equivalent in functionality for JavaScript as well:

export const descendingOrder = (x) =>

+[...("" + x)].sort((a, b) => +b - +a).join("");

This video titled "JavaScript Tips — Find the Maximum Value in an Array of Numbers" elaborates on the techniques used to derive maximum values in arrays, similar to the concept discussed here.

Another helpful resource is the video "How To Find The Max Number In An Array (Easy JavaScript Algorithm Problem)", which simplifies the process of finding maximum values in arrays.

Chapter 3: Conclusion

I’ll conclude my exploration here for today, especially as I celebrate my ninth anniversary with my wife. It's time to step away from coding and enjoy the day with her.

Thank you for reading! Be sure to keep an eye out for my next article. You can sign up for updates through my Medium email list.

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