Quick sort algorithm code

Question

I'm trying to implement a quick sort that sorts numbers and words based on the number value. I can't seem to figure out how to fix the following code to work right.

 if (high!=low&& high>low)//compares hashes and finds the number in the middle. swaps hashes and corresponding words
{

long one=hash[low];
long two=hash[high];
long three = hash[high/2];
    if((one<=two&&one>=three)||(one<=three&&one>=two))
    {
        swap(hash[low], hash[high]);
        swap(copyOfWords[low], copyOfWords[high]);
    }
    else if((three<=one&&three>=two)||(three<=two&&three>=one))
    {

        swap(hash[high/2], hash[high]);
        swap(copyOfWords[high/2], copyOfWords[high]);
    }
    else
    {

    }
    int i=low;
    int j=high-1;
    while(i!=j&&i<j)
    {

        while(hash[i]<hash[high]&&i<j)// find higher numbers and lower numbers then the middlle and swaps them
        {
            i++;
        }
        while(hash[j]>hash[high]&&i<j)
        {
            j--;
        }
        if(i==j||i>j)
        {
        }
        else
        {
            swap(hash[i],hash[j]);
            swap(copyOfWords[i],copyOfWords[j]);
            i++;
            j--;
        }
    }
        swap(hash[i],hash[high]);
    swap(copyOfWords[i], copyOfWords[high]);



    quickSort(low, j-1);//recursive
    quickSort(j+1, high);

}

}

I know the values in hash and copyOfWords are correct because when I use shell sort, it sorts them the right way. for example if there are two words, copyOfWOrds[0]="1994," and copyOfWords[1]="a" then hash[0]=549456039 and hash[1]=197000000, but the sort puts them a 1994, a instead of a 1994,. It causes more problems with more elements. Any help would be appreciated. Thanks

This would be a better question if you included example inputs and outputs. Try to describe how the code is failing, and specifically what you don't understand. — Caleb
– Caleb, Commented Feb 25, 2015 at 23:42
This would be better if you used a debugger and executed each statement singly. Also, you could compare you code to existing QuickSort implementations: QuickSort implementations — Thomas Matthews
– Thomas Matthews, Commented Feb 25, 2015 at 23:50

kuroi neko · Accepted Answer · 2015-02-26 00:10:44Z

1

Why don't you go to the quick sort wiki page and see how it's done?

Your code tries to do unnecessary stuffs and eventually trips over its own feet. Keep it simple and it will work.

And Btw Quicksort works very well on arrays, so it's a shame to make one version where the array is hard-coded.

answered Feb 26, 2015 at 0:10

kuroi neko

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2 Comments

Anonymous Over a year ago

the array isn't hard coded, it a list of words from a text file stored into the array and converts those words to hashes. Thanks for the website.

kuroi neko Over a year ago

I mean the array could be passed as an argument to quicksort. That is what hard-coded means: non configurable.

The Lost Petrol · Accepted Answer · 2025-10-11 02:32:43Z

1

One bug in your code is that you have

long three = hash[high/2];

and

swap(hash[high/2], hash[high]);
swap(copyOfWords[high/2], copyOfWords[high]);

This may louse up your sort when high/2 is not in the range low..high.

You no doubt meant to write

long three = hash[(low+high)/2];

and

swap(hash[(low+high)/2], hash[high]);
swap(copyOfWords[(low+high)/2], copyOfWords[high]);

answered Oct 11 at 2:32

The Lost Petrol

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