Section 1.1: The Challenge

Today's coding challenge is straightforward: Square Every Digit. The task is to take a number and return a new number where each digit is squared. For instance, for the number 9119, the output should be 811181, while squaring 0 results in 0.

Subsection 1.1.1: Proposed Solution

The solution I suggest is implemented in TypeScript as follows:

export class Kata {

static squareDigits(num: number): number {

const char: string = num.toString();

const result: string = [...char].map((c) => parseInt(c) ** 2).join("");

return parseInt(result);

}

}

In JavaScript, the equivalent solution would be:

function squareDigits(num) {

const char = num.toString();

const result = [...char].map((c) => parseInt(c) ** 2).join("");

return +result;

}

Section 1.2: Breaking Down the Solution

To clarify the solution, I will dissect the problem into manageable parts. Initially, I convert the number into a string format.

const char: string = num.toString();

const char = num.toString();

This conversion allows me to isolate each individual digit. I can achieve this via the toString() method or by concatenating an empty string to the number.

const char: string = "" + num;

const char = "" + num;

While the problem primarily concerns positive integers, it’s worthwhile to consider negative values as well. To handle negative numbers, I can apply the Math.abs() function to convert them to positive.

const char: string = Math.abs(num).toString();

const char = Math.abs(num).toString();

After obtaining the string representation, I can transform it into an array, allowing me to utilize the Array.map() method.

Next, I convert the string into an array using the spread operator:

const array: Array = [...char];

const array = [...char];

To square a number, I can use the exponentiation operator:

const result: number = 2 ** 3;

const result = 2 ** 3;

To convert a string back to a number, the parseInt() method comes in handy:

const result: number = parseInt("123");

const result = parseInt("123");

Lastly, to join an array into a string, I can use the Array.join() method. The final result is constructed as follows:

const result: string = [...char].map((c) => parseInt(c) ** 2).join("");

const result = [...char].map((c) => parseInt(c) ** 2).join("");

The final step is to return the computed result as a number:

return parseInt(result);