feat(2023): add solution for challenge #3

2023/challenge-03/README.md

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+# Challenge #3: The naughty elf
+
+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.
+
+```js
+const original = 'abcd'
+const modified = 'abcde'
+findNaughtyStep(original, modified) // 'e'
+
+const original = 'stepfor'
+const modified = 'stepor'
+findNaughtyStep(original, modified) // 'f'
+
+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**

2023/challenge-03/challenge-03.test.ts

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+import { describe } from 'vitest'
+import { findNaughtyStep } from './challenge-03'
+
+const TEST_CASES: TestCases<[string, string], string> = [
+  { args: ['abcd', 'abcde'], expected: 'e' },
+  { args: ['xxxx', 'xxoxx'], expected: 'o' },
+  { args: ['stepfor', 'stepor'], expected: 'f' },
+  { args: ['iiiii', 'iiiii'], expected: '' },
+]
+
+describe('Challenge #3: The naughty elf', () => {
+  buildChallengeTestCases({
+    cases: TEST_CASES,
+    spreadFn: findNaughtyStep,
+  })
+})

2023/challenge-03/challenge-03.ts

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+export function 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]) ?? ''
+}