Comments on: Friday Algorithms: Iterative Quicksort /2010/06/18/friday-algorithms-iterative-quicksort/ on web development Fri, 26 Oct 2018 21:40:18 +0000 hourly 1 https://wordpress.org/?v=5.0.3 By: John /2010/06/18/friday-algorithms-iterative-quicksort/comment-page-1/#comment-474730 Sun, 10 Dec 2017 19:27:51 +0000 /?p=1631#comment-474730 I did find a genuine bug though: The code fails if you try to sort an empty array. It turns “[]” into “[undefined]”.

]]> By: John /2010/06/18/friday-algorithms-iterative-quicksort/comment-page-1/#comment-474726 Sun, 10 Dec 2017 17:51:56 +0000 /?p=1631#comment-474726 I mean the example code has “&lt;” instead of “<“. The encoding is wrong ;P

]]> By: John /2010/06/18/friday-algorithms-iterative-quicksort/comment-page-1/#comment-474725 Sun, 10 Dec 2017 17:51:16 +0000 /?p=1631#comment-474725 @xgqfrms The only difference between your code and the article is that the article has “<” instead of proper “less than” symbols. Anyone can fix that manually be replacing them with the real “less than” bracket symbol…

@stoimen Can you edit the webserver to properly encode “less than” code symbols?

]]> By: xgqfrms /2010/06/18/friday-algorithms-iterative-quicksort/comment-page-1/#comment-435601 Thu, 22 Dec 2016 09:22:14 +0000 /?p=1631#comment-435601 https://repl.it/Ev1E/12
# javascript demo codes bugs fixed:
“`js
var a = [8, 4, 6, 2, 1, 9, 5, 5, 4, 3, 4, 3];

function qsort(arr) {
var stack = [arr];
var sorted = [];
while (stack.length) {
var temp = stack.pop(),
tl = temp.length;
if (tl == 1) {
sorted.push(temp[0]);
continue;
}
var pivot = temp[0];
var left = [],
right = [];
for (var i = 1; i < tl; i++) {
if (temp[i] < pivot) {
left.push(temp[i]);
} else {
right.push(temp[i]);
}
}
left.push(pivot);
if (right.length)
stack.push(right);
if (left.length)
stack.push(left);
}
console.log("sorted = " + sorted);
console.log("typeof = " + typeof sorted);
// return sorted[0] + "," + sorted[1] + "," + sorted[2] + "," + sorted[3] + "," + sorted[4] + "," + sorted[5] + "," + sorted[6] + "," + sorted[7] + "," + sorted[8];
}
qsort(a);

//console.log("sorted = " + qsort(a));
“`

]]> By: Mateevici /2010/06/18/friday-algorithms-iterative-quicksort/comment-page-1/#comment-16269 Fri, 06 Jul 2012 13:49:24 +0000 /?p=1631#comment-16269 Hi!

Great post!

Still, I must object to the correctness of the algorithm.
Correct me if I’m wrong, but if the pivot element is equal to the maximum of the sub-sequence, the algorithm loops forever. Just add the pivot as a separate sub-sequence to the stack and all should be fine. Right?

Have a great day!

]]> By: Stoimen /2010/06/18/friday-algorithms-iterative-quicksort/comment-page-1/#comment-14264 Wed, 20 Apr 2011 09:43:05 +0000 /?p=1631#comment-14264 @R.Arce – great example thanx!

]]> By: R. Arce /2010/06/18/friday-algorithms-iterative-quicksort/comment-page-1/#comment-14260 Tue, 19 Apr 2011 21:00:32 +0000 /?p=1631#comment-14260 In case your readers are interested, here is a c++ version..

#include 
#include 

using namespace std;

vector qs_iterative(vector & v) {
	// convert to a vector of vectors
	vector< vector  > vv;
	vector  tmp;
	vector  sorted;
	
	
	vv.push_back(v);
	
	while (!vv.empty()) {
		tmp = vv.back();
		vv.pop_back();
		if (tmp.size()==1) sorted.push_back(tmp.back());
		
		else {
			int pivot = tmp[0];
			vector  left, right;
	 
			for (int i = 1; i < tmp.size(); i++) {
				if (tmp[i]  0) vv.push_back(right);
			if (left.size()  > 0) vv.push_back(left);
			}
	}
	return sorted;
}
]]> By: David /2010/06/18/friday-algorithms-iterative-quicksort/comment-page-1/#comment-14131 Mon, 27 Dec 2010 15:58:00 +0000 /?p=1631#comment-14131 i’m sorry it did not work out:

for (var i = 1; i < tl; i++) {
            if (temp[i] < pivot) {
                left.push(temp[i]);
            } else {
                right.push(temp[i]);
            }
        }

did you mean

for (var i = 1; i < tl; i++) {
    if (temp[i] < pivot) {
]]> By: David /2010/06/18/friday-algorithms-iterative-quicksort/comment-page-1/#comment-14130 Mon, 27 Dec 2010 15:55:59 +0000 /?p=1631#comment-14130 Hi. At first, happy christmas and thanks for the work.
I’m trying to port the algorithm to c#.
Is there a problem with the following strings?

for (var i = 1; i < tl; i++) {
            if (temp[i] < pivot) {

did you mean

for (var i = 1; i < tl; i++) {
            if (temp[i] < pivot) {

?
Thanks in advance.

]]>