The solution to Challenge #3 of AdventJS 2023
The solution to the previous challenge
The solution to the next challenge
Challenge Description
In Santa's workshop, a mischievous elf has been playing around with the gift production line, adding or removing an unplanned step.
You have the original sequence of original manufacturing steps and the modified modified sequence that may include an extra step or be missing a step.
Your task is to write a function that identifies and returns the first extra step that was added or removed in the manufacturing chain. If there is no difference between the sequences, return an empty string.
const original = 'abcd'
const modified = 'abcde'
findNaughtyStep(original, modified)
const original = 'stepfor'
const modified = 'stepor'
findNaughtyStep(original, modified)
const original = 'abcde'
const modified = 'abcde'
findNaughtyStep(original, modified)
Please, keep in mind:
There will always be one different step or none.
The modification can occur anywhere in the string.
The original steps could be empty
Analysis
The goal is to write a function that can identify the first difference between two strings, either by an extra char in the string or a missing char.
💡
Char: In programming, the
char data type is for characters. It refers to a symbol (letters, numbers, punctuation) like a, +, 6, !, S. In JavaScript, it is still a string, as there is no data type for char, but when we talk about it we refer to a single character. -
MDN Glossary
Input:
Original (original): The original string, from which we must start to find the differences. These are the original steps.
Modified (modified): The modified string to which we must find the first extra char or the first missing char. These are the steps modified by the mischievous elf.
Output:
- A string showing the extra or missing char, if not found returns an empty string
''
Considerations
- The modified sequence must not only contain the chars from the original but also have them in the same order.
Solution
You can use a loop to compare char by char in the strings and, upon finding the difference, evaluate whether it is an extra element or a missing element and return it. If the conditions are not met, we return an empty string ''.
Code
function findNaughtyStep(original, modified) {
let i = 0;
while (i < original.length || i < modified.length) {
if (original[i] !== modified[i]) {
return original.length > modified.length ? original[i] : modified[i];
}
i += 1;
}
return '';
}
Solution by Achalogy:
findNaughtyStep(original, modified) {
const [lessWords, mostWords] =
[original, modified].sort((a, b) => a.length - b.length)
return [...mostWords].find((x, i) => lessWords[i] != x) ?? "";
}
Solution by iswilljr:
findNaughtyStep(original: string, modified: string) {
const originalLen = original.length
const modifiedLen = modified.length
const sequences = {
[originalLen]: [original, modified],
[modifiedLen]: [modified, original],
}
const [steps, reference] = sequences[Math.max(originalLen, modifiedLen)]
return [...steps].find((step, index) => step !== reference[index]) ?? ''
}
And that was the challenge for December 3rd and its solutions. Do you have another alternative solution? Leave it in the comments!
