Selection Sort in JavaScript

Question

function newsort(arr, left, right){    

for(var i= left; i < right; ++i){
    var min = i;
    for (var j = i; j < right; ++j){
        if (arr[min] > arr[         


        

Answer 1

Eloquent solution:

const selectionSort = (items) => {
  items.forEach((val, i, arr) => {
    const smallest = Math.min(...arr.slice(i))
    const smallestIdx = arr.indexOf(smallest)

    if (arr[i] > arr[smallestIdx]) {
      const temp = arr[i]
      arr[i] = arr[smallestIdx]
      arr[smallestIdx] = temp
    }
  })

  return items
}

Standard solution:

const selectionSort = (arr) => {
  for (let i=0; i <= arr.length-1; i++) {
    // find the idnex of the smallest element
    let smallestIdx = i

    for (let j=i; j <= arr.length-1; j++) {
      if (arr[j] < arr[smallestIdx]) { 
        smallestIdx = j
      }
    }

    // if current iteration element isn't smallest swap it
    if (arr[i] > arr[smallestIdx]) {
      let temp = arr[i]
      arr[i] = arr[smallestIdx]
      arr[smallestIdx] = temp
    }
  }

  return arr
}

Testing:

console.log( // [14, 29, 56, 72, 92, 98] 
  selectionSort([29, 72, 98, 14, 92, 56]) 
)

Answer 2

function selectionSort(arr) {

    var temp = 0;
    for (var i = 0; i < arr.length; ++i) {
        for (var j = i + 1; j < arr.length; ++j) {
            if (arr[i] > arr[j]) { // compare element with the reset of other element
                temp = arr[i];  // swap the valuse from smallest to gretest
                arr[i] = arr[j];
                arr[j] = temp;
            }
        }
    }
    return (arr);
}

selectionSort([4,6,5,3,7,9]);

Answer 3

The selection sort algorithm says: repeatedly find the minimum of the unsorted array.

Recursive approach

1. Find the minimum number and its index/position
2. Remove the min item from the array and append it at the end of the same one
3. After each iteration, when finding the minimum provide the unsorted array (if not you will again get the previous minimum). See argument of Math.min

Note: the second argument of selectionSort (i) is needed in order to sort elements of the unsorted array

function selectionSort(arr, i) {
  if (i === 0) {
    return arr;
  }
  const min = Math.min(...arr.filter((x, j) => j < i));
  const index = arr.findIndex(x => x === min);
  arr.splice(index, 1);
  arr.push(min);
  return selectionSort(arr, --i);
}

const unsortedArr = [5, 34, 5, 1, 6, 7, 9, 2, 100];
console.log('result', selectionSort(unsortedArr , unsortedArr.length))

Answer 4

The problem with your code is that the left and right parameters are passed in the wrong way round. Here is the working code:alert(newsort(arr, 0 ,arr.length));

Answer 5

You are basically doing the selection start is reverse order which will not work.

Your left should begin with 0 and right should end with arr.length.

newsort(arr, 0 ,arr.length); this should work.

Check out this link if you want to implement selection sort in javascript.

https://learnersbucket.com/examples/algorithms/selection-sort-in-javascript/

Answer 6

var selectionSort = function(array){
  for(var i = 0; i < array.length; i++){
    //set min to the current iteration of i
    var min = i;
    for(var j = i+1; j < array.length; j++){
      if(array[j] < array[min]){
       min = j;
      }
    }
    var temp = array[i];
    array[i] = array[min];
    array[min] = temp;
  }
  return array;
};
var array = [3,2,10,1]
console.log('selectionSort should return [1,2,3,10]-->',selectionSort(array));

It might be easier to reason with if you use a helper swap function:

//HELPER FUNCTION
var swap = function(array, firstIndex, secondIndex){
    var temp = array[firstIndex];
    array[firstIndex]  = array[secondIndex];
    array[secondIndex] = temp;
};
var array = [2,1];
swap(array, 0, 1)
console.log('swap should return [1,2] -->', array);


var selectionSort = function(array){
  for(var i = 0; i < array.length; i++){
    //set min to the current iteration of i
    var min = i;
    for(var j = i+1; j < array.length; j++){
      if(array[j] < array[min]){
        min = j;
      }
    }
    swap(array, i, min);
  }
  return array;
};
var array = [3,2,10,1]
console.log('selectionSort should return [1,2,3,10]-->',selectionSort(array));

Visual of selection sort:

[3,1,2]
 |-----> iterate over list. find that min = 1 so we swap current i (3) with min(1)

[1,3,2]
   |---> iterate over list. find that min = 2 so we swap current i (3) with min(2)

[1,2,3]
     |---> iterate over list. find that min = 3 so we swap current i (3) with min(3)