Home Discussion Discuss: Quick Sort In Java

thank you

• ### Bug?Jing May 25, 2011 at 12:26 AM

Hi I think there is a problem in your implementation. Try {12,9,30,99,30,1,30,10,13}; The point is if there are more than one occurrences of the pivot and they are in symmetric positions then there is a problem. Please point out if I'm wrong. Thanks Jing

i like this

• ### This is incorrectSebastian June 24, 2011 at 1:46 AM

This is an incorrect implementation of Quick Sort. The algorithm fails for inputs such as this: 68 13 56 44 82 78 59 78 61 82

• ### No duplicatesDavid September 22, 2011 at 7:22 PM

Hi, Fantastic short and easy to remember algorithm but it does not allow duplicate entires. For example, in your code you use the data: {12,9,4,99,120,1,3,10,13}; However, {12,9,4,99,120,1,3,10,13,13}; fails due to the extra 13. Any chance you could update the algorithm? David

• ### quicksortjoseph October 13, 2011 at 9:52 AM

hays gays i want to learn more about more details about QUICK SORT because this my project in are school just for give me because this my for my future thank you..

• ### Unable to run codeKaushalendra January 2, 2012 at 5:13 PM

kindly try to run this code for { 1, 3, 6, 4, 1, 8, 3, 9, 2, 0, 1 } I am not able to run it . It goes in an infinite loop

• ### DudaMartin Hernandez Gonzalez January 13, 2012 at 10:32 AM

What happen if two numbers be repeated? thanks for your explication...

• ### Incorrect implementationVivek January 17, 2012 at 11:47 PM

The implementation is incorrect. It fails for input 1,2,3,4,8,9,76,54,58,50,322,11,44,11

• ### changing the output of the quick sort.riz January 24, 2012 at 6:20 AM

please help me in getting the output in this fashion. using array the below example is using link list though. but i need it in arrays. please modify the above program so that i can get the following output. Initial List: 5 -> 9 -> 2 -> 9 -> 7 -> null Level 0: Before Left: 2 -> null Level 0: Before Pivot is: 5 Level 0: Before Right: 9 -> 9 -> 7 -> null Level 1: Before Left: 7 -> null Level 1: Before Pivot is: 9 Level 1: Before Right: 9 -> null Level 1: After Left: 7 -> null Level 1: After Pivot is: 9 Level 1: After Right: 9 -> null Level 0: After Left: 2 -> null Level 0: After Pivot is: 5 Level 0: After Right: 7 -> 9 -> 9 -> null Sorted List: 2 -> 5 -> 7 -> 9 -> 9 -> null

• ### algorithms and datastructuresm.nadipi naganna March 15, 2012 at 5:34 PM

u r services is very excellent.

• ### codeC: May 7, 2012 at 11:39 AM

helped alot thanks

• ### more than 2 numbers are equal!!Nguyen Chi Vien June 2, 2012 at 12:17 AM

please test with: array[] = {12,99,4,99,120,1,3,10,13}; loop loop and loop... need to change: while (lo<hi && array[hi] > mid) { ----> while (lo<hi && array[hi] >= mid) {

• ### algo review..Raj June 8, 2012 at 5:01 PM

I think this description of quick sort is very complicated. The algo is simple. take pivot, put all smaller items in left and bigger items in right. repeat same thru recursion...

• ### try this code for....{11,12,12,1}varun June 30, 2012 at 12:17 AM

try this code for....{11,12,12,1}..there is some issue....loop is not breaking....

• ### This is a bad implementation of quick sort!Matt July 1, 2012 at 5:55 AM

Use {0,0,0} as the input and it will loop forever! Shame on you.

• ### solution doesnt workAmit July 10, 2012 at 10:23 PM

Hangs for the input 9 7 7 2 2 3

title

• ### There is some problem in the above codeArumugam August 8, 2012 at 10:15 AM

try this Array int array[] = { 1,2, 8, 2, 6, 0, 11, 13, 3, 4 };

• ### this code fails for duplicate valuesAfsar Ali August 31, 2012 at 8:52 PM

this code fails for duplicate values

• ### ExceptionIvan Garcia October 9, 2012 at 9:08 PM

I was using your method, but I found an exception, the programm hangs out when we have for example an array: 12,9,4,99,12,1,3,10,13 where there are two number 12. I'd would like to know why it's happening when we execute that? Thanks in advantage. Kind Regards.

• ### Not working fineRaul November 11, 2012 at 8:22 AM

Try this array : int array[] = {-12, 9, 4, 99, 120, -1, 3, 10, -1}; int array[] = {-12, 9, 4, 99, 120, -1, 3, 10, -12}; recursion does not finish with negative numbers in some cases and even with positive numbers like this : int array[] = {120, 9, 4, 99, 120, 1, 3, 10, 120}; //does not finish Fix it.

• ### Not as explainedANdres Luque March 26, 2013 at 11:06 AM

Hello, if you print each step of the quicksort method you will see that the steps of finding the high value and swaping are wrong

• ### ExplanationMario April 14, 2013 at 7:33 PM

Please can you explain me: quick_srt(array, low, lo); quick_srt(array, lo == low ? lo+1 : lo, n); Thanks in advance.

• ### for those who faces problem with duplicate entrieswaheduzzaman June 16, 2013 at 7:03 PM

just place an 'if' condition to check whether it has the same value or not. If there is a match just let it where it is..otherwise let it execute other condition.. The code should be like: public static void quick_sort(......){ ................. ........... .................... ............. if(array[hi]==array[lo]){ //here do nothing } if (lo < hi) { int T = array[lo]; array[lo] = array[hi]; array[hi] = T; } if (lo < hi) { int T = array[lo]; array[lo] = array[hi]; array[hi] = T; } } hope this will help... thanks

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• ### Bug Fixediano90 November 18, 2013 at 10:38 PM

along with the help of a tutor in college we managed to solve the problem where reoccurring values would cause an infinite loop. This was due to a missing counters within the if statement at the end of a while loop. This was causing the loop while loop to freeze. The correct code should be: while (lo < hi) { while (lo<hi && array[lo] < mid) { lo++; } while (lo<hi && array[hi] > mid) { hi--; } if (lo < hi) { int T = array[lo]; array[lo] = array[hi]; array[hi] = T; lo++; hi--; } }

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