CODEWITHSUNDEEP
c#algorithmquicksort
Elgahir
Elgahir

Reputation: 57

My program quicksort does not work

I've problem with my implementation of quick sort. Problem looks randomly and the sorted array is never sorted.

I based on this pseudocode:

1 procedure quick sort1(l, r);
2 begin
3 if ` < r then
4 t ← A[l]; {t — pivot}
5 s ← l;
6 for i ← l + 1 to r do {move elements around pivot}
7 if A[i] < t then
8 s ← s + 1;
9 swap(A[s], A[i]);
10 end if;
11 end for;
12 swap(A[l], A[s]);
13 quick sort1(l, s − 1); {recursive call for both subarrays}
14 quick sort1(s + 1, r);
15 end if;
16 end.

There is my code:

    public void QuickSort(int[] A, int l, int r)
    {
        int t;
        int s = 0;
        if (l < r)
        {
            t = A[l];
            s = l;
            for (int i = l + 1; i < r; i++)
            {
                if (A[i] < t)
                {
                    s = s + 1;
                    swaponator(ref A[s], ref A[i]);

                }
            }
            swaponator(ref A[l], ref A[s]);
            QuickSort(A, l, s - 1);
            QuickSort(A, s + 1, r);
        }

    }

but it does not work - i have no idea why, i debug this and still nothing.

please, can someone give me a tip?

Best regards.

Upvotes: 1

Views: 186

Answers (2)

Prateek Mirdha
Prateek Mirdha

Reputation: 67

Their might be problem if duplicate entries are there, so

if (A[i] <= t);

and r should be passed as 'n-1' initially.

Upvotes: 0

ZanAl
ZanAl

Reputation: 73

The problem is in the for loop. To iterate all the numbers in the array, the variable i must reach the value of r.

for (int i = l + 1; i <= r; i++)

Upvotes: 1

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