sorting an array in descending order in javascript without using any built-in method

Question

I need to sort a simple array in descending order in javaScript without using a built-in method and it took me way too much time already... please help

function dscSort(array) {
    for (var i = 1; i < array.length; i++) {
        var tmp = array[i];
        for (var j = i - 1; j >= 0 && (array[j] < array[i]); j--) {
            array[j + 1] = array[j];
        }
        array[j + 1] = tmp;
    }
    return array;
}

like i cant use array.sort(), but have to write it like i just did, but its not working — Mary
– Mary, Commented Apr 14, 2017 at 21:42
Why don't you check out quick sort. en.wikipedia.org/wiki/Quicksort — inoabrian
– inoabrian, Commented Apr 14, 2017 at 21:55
I'm assuming this is a school assignment? In which case, they are most likely looking for a Bubble Sort solution — mhodges
– mhodges, Commented Apr 14, 2017 at 22:01

trincot · Accepted Answer · 2017-04-15 09:07:45Z

3

The approach is correct. You just had a tiny bug in the code. Instead of this:

for (var j = i - 1; j >= 0 && (array[j] < array[i]); j--) {

Do this:

for (var j = i - 1; j >= 0 && (array[j] < tmp); j--) {

This is necessary, because the value at array[i] might get overwritten with array[i-1] at the first iteration, and so in the next iteration you would be looking at the wrong value.

answered Apr 15, 2017 at 9:07

trincot

357k38 gold badges282 silver badges338 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Krishna · Accepted Answer · 2019-08-29 19:08:56Z

You can create one for yourself like the one below. Syntax for using this

let numbSet = [44,55,22,55,44,11];
Ascending by default numbSet.sorty();
Descending numbSet.sorty('dsc');

If an array of objects then pass the key like

let objSet = [{a:44},{a:55},{a:22},{a:55},{a:44},{a:11}];
objSet.sorty('asc', 'a');

let numbSet = [44, 55, 22, 55, 44, 11];
let objSet = [{
  a: 44
}, {
  a: 55
}, {
  a: 22
}, {
  a: 55
}, {
  a: 44
}, {
  a: 11
}];

Array.prototype.sorty = function(type, key) {
  if(this.length) {
    if (type === 'dsc') {
      return recuDsc(this, this.length - 1, key ? key : false);
    } else {
      // default assending    
      return recuAsc(this, 0, key ? key : false);
    }
  }
  return this;
}

function recuAsc(arry, indx, key) {
  let arryLength = arry.length;
  let isSmaller = false;
  let a, b, i = indx + 1;
  if (indx != (arryLength - 1)) {

    for (i; i < arryLength; i++) {
      a = arry[indx];
      b = arry[i];

      isSmaller = key ? a[key] < b[key] : a < b;

      if (!isSmaller) {
        arry[indx] = b;
        arry[i] = a;
      }
    }
    recuAsc(arry, indx + 1, key ? key : false);
  }
  return arry;
}

function recuDsc(arry, indx, key) {
  let arryLength = arry.length;
  let isSmaller = false;
  let a, b, i = indx - 1;
  if (indx != (0)) {
    for (i; i >= 0; i--) {
      a = arry[indx];
      b = arry[i]
      isSmaller = key ? a[key] < b[key] : a < b;

      if (!isSmaller) {
        arry[indx] = b;
        arry[i] = a;
      }
    }
    recuDsc(arry, indx - 1, key ? key : false);
  }
  return arry;
}

console.log('Sorty an Array of numbers, ascending');
console.log(numbSet.sorty());
console.log('Sorty an Array of numbers, descending');
console.log(numbSet.sorty('dsc'));
console.log('Sorty an Array of Object');
console.log(objSet.sorty('asc', 'a'))

Collectives™ on Stack Overflow

sorting an array in descending order in javascript without using any built-in method

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related