Can you provide tips on using a recursive function to combine elements of the first array with elements of other arrays?

Question

Can you provide tips on using a recursive function to combine elements of the first array with elements of other arrays?

Let's consider the following scenario: I have an array

arr=[1,3,7,8];
The 1st call will yield: [4,8,9]
The 2nd Call will yield:[12,13]
The 3rd call will result in:[25]

How can this be achieved using recursion in JavaScript?

javascript arrays recursion

Answer 1

Answer №1

You need to consider 3 scenarios

For an empty array, the result should be an empty array
For an array with only one element, return the same array
If the array has 2 or more elements, return a new array with each element added to the previous

const foo = ([x,...xs]) => {
  if (x === undefined)
    return []
  else if (xs.length === 0)
    return [x]
  else
    return foo(xs.map(y => x + y))
}

console.log(foo([]))        // []
console.log(foo([1]))       // [1]
console.log(foo([1,3]))     // [4]
console.log(foo([1,3,7]))   // [12]
console.log(foo([1,3,7,8])) // [25]

The function can be enhanced by separating concerns and creating helper functions

const add = x => y => x + y

const isEmpty = xs => xs.length === 0

const isNull = x => x == null

const foo = ([x,...xs]) => {
  if (isNull(x))
    return []
  else if (isEmpty(xs))
    return [x]
  else
    return foo(xs.map(add(x)))
}

console.log(foo([]))        // []
console.log(foo([1]))       // [1]
console.log(foo([1,3]))     // [4]
console.log(foo([1,3,7]))   // [12]
console.log(foo([1,3,7,8])) // [25]

Answer 2

You need to consider 3 scenarios

For an empty array, the result should be an empty array
For an array with only one element, return the same array
If the array has 2 or more elements, return a new array with each element added to the previous

const foo = ([x,...xs]) => {
  if (x === undefined)
    return []
  else if (xs.length === 0)
    return [x]
  else
    return foo(xs.map(y => x + y))
}

console.log(foo([]))        // []
console.log(foo([1]))       // [1]
console.log(foo([1,3]))     // [4]
console.log(foo([1,3,7]))   // [12]
console.log(foo([1,3,7,8])) // [25]

The function can be enhanced by separating concerns and creating helper functions

const add = x => y => x + y

const isEmpty = xs => xs.length === 0

const isNull = x => x == null

const foo = ([x,...xs]) => {
  if (isNull(x))
    return []
  else if (isEmpty(xs))
    return [x]
  else
    return foo(xs.map(add(x)))
}

console.log(foo([]))        // []
console.log(foo([1]))       // [1]
console.log(foo([1,3]))     // [4]
console.log(foo([1,3,7]))   // [12]
console.log(foo([1,3,7,8])) // [25]

Answer 3

Answer №2

It may seem unusual to tackle this problem recursively, but here's a unique approach -

function calculateTotal(numbers){
  // base case
  if(numbers.length === 1 || numbers.length === 0) {
    return numbers
  } else {
    return calculateTotal(numbers.slice(1).map(element => element + numbers[0]))
  }
}

Answer 4

It may seem unusual to tackle this problem recursively, but here's a unique approach -

function calculateTotal(numbers){
  // base case
  if(numbers.length === 1 || numbers.length === 0) {
    return numbers
  } else {
    return calculateTotal(numbers.slice(1).map(element => element + numbers[0]))
  }
}

Can you provide tips on using a recursive function to combine elements of the first array with elements of other arrays?

Answer №1

Answer №2

Similar questions

Achieve iframe resizing using only pure JavaScript, no reliance on jQuery required

My custom function is not invoking the Firebase function createUserWithEmailAndPassword

Having Trouble Deploying NextJS Site on Gh-Pages Despite Using basePath and assetPrefix

I am struggling to retrieve the data from the Giphy API after making the initial AJAX request

What is the best way to use form input to filter an Observable?

When using React Router, make sure to set the navigation tab's style class to "active" if you are

A secure method for dynamically adding a JavaScript file

Navigating through a predetermined list of HTML pages with next and previous options

How can I incorporate a feature in my Angular application that allows users to switch between different view types, such as days, using JavaScript

Finding and removing the replicated keys within a JSON array while also retrieving the corresponding JSON path

The functionality of jQuery is limited when trying to implement the .has() method

Tips for creating a console.log wrapper specifically designed for Angular2 using Typescript

Error encountered: The fiber texture failed to load due to a component becoming suspended during the response to synchronous input

Ensure that properties return arrays and nested dictionaries - CA1819

Listener of events that is modifying the incorrect label

Managing field placement as the table height grows: tips and tricks

Ways to boost an array index in JavaScript

How can I simulate keyboard events in Angular using a button click?

What is the reason for choosing the term "shadow" over "override" in JavaScript?

What methods can be used to maintain the selected date when the month or year is changed in the react-datepicker component of reactjs?