[FIXED] How to sort an array of integers based on its binary representation in JavaScript?

Issue

Problem title: Binary Sort Ascending:

I have a task which consists of creating a function in JavaScript which orders an array that receives a list of unordered integers. The function must return an ordered array of integers according to the following criteria:

1. The greater number of ones in the binary representation of the integer, the closer to the index 0 the element should be.
2. In case two or more numbers have the same number of ones in their binary representation, the decimal number of lesser value will be closer to the beginning.

Example:

For the entry: [1, 15, 5, 7, 3]

The return should be: [15, 7, 3, 5, 1]

Explanation:

Decimal = Binary

• 1 = 1
• 15 = 1111
• 5 = 101
• 7 = 111
• 3 = 11

The decimal number whose binary representation contains plus ones is 15 (1111 in binary), so it will go first in the array (index = 0). Then go on the 7, with three (111) ones in its binary representation.

Then there are 2 numbers whose binary representation contains the same number of ones, these decimals are 5 (101) and 3 (11), both with 2 ones. In this case, it will go first (closer to index = 0) the 3, because it's decimal representation is smaller (3 < 5).

Solution:

Finally, I have found a way to solve this task:

const binaryOnes = integerArr => {

  let binaryArray = integerArr.map(num => num.toString(2))

  binaryArray.sort((a, b) => {

    let regEx = /1/g
    let A = a.match(regEx).length
    let B = b.match(regEx).length

    if (A < B) return 1
    else if (A > B) return -1
    else {
      let binaryToIntegerA = parseInt(A, 2)
      let binaryToIntegerB = parseInt(B, 2)

      if (binaryToIntegerA < binaryToIntegerB) return -1
      else return 1
    }
    
  })

  return binaryArray.map(num => parseInt(num, 2))

}

binaryOnes([1,15,5,7,3]) // [ 15, 7, 3, 5, 1 ]

Please if anyone finds a better way to solve it, I will appreciate.

Also some feedback of this post (is my first question on StackOverflow)

Thanks!

Solution

You can convert a number into binary (string type) with something like

var binary = 134.toString(2);

Then, implement the comparison function between two numbers with

function binaryCompare(a, b) {
    a = a.binary;
    b = b.binary;
    //...
}

After that, just call

[1,2,34,342]
.map( a => ({value:a, binary: a.toString(2))
.sort(binaryCompare)
.map( v => v.value );

As I don't understand your goal, I cannot implement the sort function. Hope it helps

Answered By - farvilain

Answer Checked By - Pedro (PHPFixing Volunteer)