-1

function quicksort(items){
  if((items.length)<=1){
    return(items);
  }
  point1 = 0;
  point2 = ((items.length)-1);
  while(point1 != point2){
    if(((items[point1] < items[point2]) &&(point1>point2)) || ((items[point1] > items[point2]) && (point1 < point2))){
      var temp = items[point1];
      items[point1] = items[point2];
      items[point2] = temp;
      var temp2 = point1;
      point1 = point2;
      point2 = temp2;
    }
    if(point1<point2){
      point1 = point1 + 1;
    }else{
      point1 = point1 - 1;
    }
  }
  var left = quicksort(items.slice(0,point1));
  var right = quicksort(items.slice((point1+1),items.length));
  var x  = [];
  x.concat(left,[items[point1]],right);
  return(x);
}
var x = (quicksort([5,4,3,2,1,8,19,7,100,6]));
console.log(x);

I don't understand why my quicksort implementation doesn't work I would appreciate some fresh eyes to find out the Issue(s)

Hc Hc
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  • `x.concat(left,[items[point1]],right);` creates and returns *a new array*, it does not mutate the current array. – VLAZ Feb 13 '22 at 20:22
  • @VLAZ I changed that but It still doesn't seem to work It gave an empty array before but now it gives a massive array – Hc Hc Feb 13 '22 at 20:30
  • I doubt this is the only error you have. It was just the first one I noticed. I suggest you debug your code to narrow down what goes wrong and why. [How to debug small programs](https://ericlippert.com/2014/03/05/how-to-debug-small-programs/) and [What is a debugger and how can it help me diagnose problems?](https://stackoverflow.com/q/25385173) – VLAZ Feb 13 '22 at 20:35
  • `point2` - the pivot index - should not change in the partitioning loop, and `point1` should never have to decrease. – 500 - Internal Server Error Feb 14 '22 at 10:18

1 Answers1

0

I rewrote it and it works now, for anyone in the future:

function quicksort(items){
  if((items.length)<=1){
    return(items);
  }
  var pointer1 = 0;
  var pointer2 = (items.length -1);
  while(pointer1 != pointer2){
    if(((items[pointer1]>items[pointer2])&&(pointer1<pointer2)) || (((items[pointer2])>items[pointer1]) && (pointer2<pointer1))){
      var temp = items[pointer1];
      items[pointer1] = items[pointer2];
      items[pointer2] = temp;
      var temp2 = pointer1;
      pointer1 = pointer2;
      pointer2 = temp2;
    }
    if (pointer1<pointer2){
      pointer1+=1;
    }else{
      pointer1-=1;
    }
  }
  var left = quicksort((items.slice(0,pointer1)));
  var right = quicksort((items.slice((pointer1+1),(items.length))));
  return(left.concat([items[pointer1]],right));
}
console.log(quicksort([5,4,3,2,1]));
Hc Hc
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  • 2