CODEWITHSUNDEEP
javascriptarrayssorting
Олег Якунин
Олег Якунин

Reputation: 130

Sorting array from given index

Let's assume I have a simple array

const simpleArray = [1, 2, 3, 4, 5];

In case of, for example, I want to create a carousel and connect dots to click events in Vue or React. So clicking on a dot I want to sort my array so first slide will be the slide with the index of the dot. Hence if the index of the dot is 3 - my array should look like this now

const updatedSimpleArray = [3, 4, 5, 1, 2];

With this idea in mind I came to conclusion of creating this method.

const sortedArray = (pos) =>  {

  // pos is the dot index of the dot
  // if index is 1 - simply sort the array
  if ( pos == 1 ) return arr.sort();

  // otherwise - create two separate arrays and concat them
  const firstArr = arr.filter(el => el >= pos);
  const secondArr = arr.filter(el => el < pos);
  const newArr = [...firstArr, ...secondArr];
  return newArr;
}

What do you think about my approach and time/memory complexity? Would you use another approach?

EDIT

There is a problem if my array is not sorted. If it looks like this

const array = [4, 5, 1, 2, 3]

Whole function is not working correctly. My thoughts - sort it first and then filter/splice on given index?

Upvotes: 2

Views: 260

Answers (3)

Олег Якунин
Олег Якунин

Reputation: 130

Combining knowledge from Harish' answer I refactored the algorithm. Now it works with both examples, where arrays can look like this.

const array1 = [1, 2, 3, 4, 5]
const array2 = [4, 5, 1, 2, 3]

So here goes the function

const sortedArray = (pos) =>  {
  // First of all - sort the array
  const newArr = arr.sort((a, b) => a - b);

  // and then splice it and add this part to the start of the array
  newArr.unshift(...newArr.splice(pos-1));
  return newArr;
}

Upvotes: 1

Harish
Harish

Reputation: 1911

You can do like, remove the elements from your index to length of the array and push it to start of the same array

    const array = [1, 2, 3, 4, 5];
    const index = 2;
    array.unshift(...array.splice(index))
    
    console.log(array)

Upvotes: 4

adiga
adiga

Reputation: 35263

You could get the index of the current dot value. Then create an array with 2 iterations of the original array using [...array, ...array]. For the given array, it will look like [1, 2, 3, 4, 5, 1, 2, 3, 4, 5]. Then use slice to get array.length items starting from index

function getRotation(array, value) {
  const index = array.indexOf(value);
  return [...array, ...array].slice(index, index + array.length)
}

console.log(getRotation([1, 2, 3, 4, 5], 3))
console.log(getRotation([1, 2, 3, 4, 5], 5))

Upvotes: 1

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