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113 changes: 113 additions & 0 deletions
2024/23-encuentra-los-numeros-perdidos/README.md
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| # Reto 23: Encuentra-los-numeros-perdidos | ||
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| Los elfos están trabajando en un sistema para verificar las listas de regalos de los niños 👧👦. Sin embargo, ¡algunas listas están incompletas y **faltan números**! | ||
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| Tu tarea es escribir **una función que, dado un array de números, encuentre todos los números que faltan entre 1 y n** (donde n es el tamaño del array o el número más alto del array). | ||
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| Eso sí, ten en cuenta que: | ||
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| - Los números pueden aparecer más de una vez y otros pueden faltar | ||
| - El array siempre contiene números enteros positivos | ||
| - Siempre se empieza a contar desde el 1 | ||
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| ```js | ||
| findMissingNumbers([1, 2, 4, 6]) | ||
| // [3, 5] | ||
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| findMissingNumbers([4, 8, 7, 2]) | ||
| // [1, 3, 5, 6] | ||
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| findMissingNumbers([3, 2, 1, 1]) | ||
| // [] | ||
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| findDisappearedNumbers([5, 5, 5, 3, 3, 2, 1]) | ||
| // [4] | ||
| ``` | ||
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| ## Mi solución explicada | ||
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| **NOTA** Para correr este código necesitas la versión 22 o superior de Node.js. En caso contrario, puedes crear una función `difference` que haga lo mismo que `Set.prototype.difference`. | ||
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| ```js | ||
| Set.prototype.difference = function (set) { | ||
| return new Set([...this].filter((x) => !set.has(x))); | ||
| }; | ||
| ``` | ||
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| ```js | ||
| function findMissingNumbers(nums) { | ||
| const maxNumber = Math.max(...nums); | ||
| const fullSetOfNumbers = new Set( | ||
| Array.from({ length: maxNumber }, (_, index) => index + 1), | ||
| ); | ||
| const uniqueNumbers = new Set(nums); | ||
| const missingNumbers = fullSetOfNumbers.difference(uniqueNumbers); | ||
| return [...missingNumbers]; | ||
| } | ||
| ``` | ||
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| Para resolver este reto, utilice diferencia de conjuntos. Esto consiste en crear un conjunto con todos los números del 1 al número más alto del array, luego crear un conjunto con los números únicos del array y finalmente obtener la diferencia entre ambos conjuntos. | ||
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| Para esto utilice el método `Math.max` para obtener el número más alto del array, luego cree un conjunto con todos los números del 1 al número más alto del array utilizando `Array.from` y `Set`. Después cree un conjunto con los números únicos del array utilizando `Set`. Finalmente obtuve la diferencia entre ambos conjuntos y devolví un array con los números faltantes. | ||
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| **Veamos un ejemplo**: | ||
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| Supongamos que tenemos el siguiente array: | ||
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| ```js | ||
| const nums = [1, 2, 4, 6]; | ||
| ``` | ||
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| Primero obtenemos el número más alto del array, en este caso es el número 6: | ||
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| ```js | ||
| const maxNumber = Math.max(...nums); | ||
| // const maxNumber = Math.max(...[1, 2, 4, 6]); | ||
| // const maxNumber = Math.max(1, 2, 4, 6); | ||
| const maxNumber = 6; | ||
| ``` | ||
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| Luego creamos un conjunto con todos los números del 1 al número más alto del array, para este caso utilizamos `Array.from` y `Set`, donde `Array.from` crea un array con los números del 1 al 6 y `Set` convierte ese array en un conjunto: | ||
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| ```js | ||
| const fullSetOfNumbers = new Set( | ||
| Array.from({ length: maxNumber }, (_, index) => index + 1), | ||
| ); | ||
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| // Array.from({ length: 6 }, (_, index) => index + 1); | ||
| // Array.from([undefined, undefined, undefined, undefined, undefined, undefined], (_, index) => index + 1); | ||
| // [1, 2, 3, 4, 5, 6] | ||
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| // new Set([1, 2, 3, 4, 5, 6]); | ||
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| const fullSetOfNumbers = new Set([1, 2, 3, 4, 5, 6]); | ||
| ``` | ||
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| Después creamos un conjunto con los números únicos del array, para este caso utilizamos `Set`: | ||
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| ```js | ||
| const uniqueNumbers = new Set(nums); | ||
| // const uniqueNumbers = new Set([1, 2, 4, 6]); | ||
| const uniqueNumbers = new Set([1, 2, 4, 6]); | ||
| ``` | ||
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| Finalmente obtenemos la diferencia entre ambos conjuntos, para esto utilizamos el método `difference` que creamos previamente: | ||
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| ```js | ||
| const missingNumbers = fullSetOfNumbers.difference(uniqueNumbers); | ||
| // const missingNumbers = [1, 2, 3, 4, 5, 6].difference([1, 2, 4, 6]); | ||
| // const missingNumbers = [3, 5]; | ||
| const missingNumbers = [3, 5]; | ||
| ``` | ||
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| `difference` lo que hace es obtener la diferencia entre ambos conjuntos, es decir, los números que están en el primer conjunto pero no en el segundo. Por ejemplo: la diferencia de elementos que esta en `fullSetOfNumbers` pero no en `uniqueNumbers`, es decir, si `fullSetOfNumbers` es `[1, 2, 3, 4, 5, 6]` y `uniqueNumbers` es `[1, 2, 4, 6]`, entonces la diferencia es `[3, 5]`, que son los números faltantes. | ||
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| Y devolvemos un array con los números faltantes: | ||
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| ```js | ||
| return [...missingNumbers]; | ||
| // return [3, 5]; | ||
| return [3, 5]; | ||
| ``` | ||
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| Así es como resolví este reto utilizando diferencia de conjuntos 🎉 |
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2024/23-encuentra-los-numeros-perdidos/index.js
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| /* eslint-disable func-names */ | ||
| /* eslint-disable no-extend-native */ | ||
| Set.prototype.difference = function (set) { | ||
| return new Set([...this].filter((x) => !set.has(x))); | ||
| }; | ||
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| // La función de set.difference() esta disponible desde la version 22 de nodejs | ||
| // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/difference#browser_compatibility | ||
| // Para poder utilizarla en versiones anteriores de nodejs, se debe de agregar la función al prototipo de Set | ||
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| function findMissingNumbers(nums) { | ||
| const maxNumber = Math.max(...nums); | ||
| const fullSetOfNumbers = new Set( | ||
| Array.from({ length: maxNumber }, (_, index) => index + 1), | ||
| ); | ||
| const uniqueNumbers = new Set(nums); | ||
| const missingNumbers = fullSetOfNumbers.difference(uniqueNumbers); | ||
| return [...missingNumbers]; | ||
| } | ||
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| module.exports = findMissingNumbers; |
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2024/23-encuentra-los-numeros-perdidos/index.test.js
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| const findMissingNumbers = require('./index'); | ||
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| describe('23 => Encuentra-los-numeros-perdidos', () => { | ||
| const TEST_CASES = [ | ||
| { | ||
| input: [1, 2, 4, 6], | ||
| output: [3, 5], | ||
| }, | ||
| { | ||
| input: [4, 8, 7, 2], | ||
| output: [1, 3, 5, 6], | ||
| }, | ||
| { | ||
| input: [3, 2, 1, 1], | ||
| output: [], | ||
| }, | ||
| { | ||
| input: [5, 5, 5, 3, 3, 2, 1], | ||
| output: [4], | ||
| }, | ||
| { | ||
| input: [1, 2, 3, 4, 5], | ||
| output: [], | ||
| }, | ||
| ]; | ||
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| it('should return an array', () => { | ||
| const result = findMissingNumbers([1, 2, 4, 6]); | ||
| expect(Array.isArray(result)).toBe(true); | ||
| }); | ||
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| it.each(TEST_CASES)( | ||
| 'should return the missing numbers', | ||
| ({ input, output }) => { | ||
| const result = findMissingNumbers(input); | ||
| expect(result).toEqual(output); | ||
| }, | ||
| ); | ||
| }); |
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