Quick Sort problem..

[gaurav_13191]

I have the following code for Quick Sort procedure:

#include<stdio.h>

void Quick_sort(int *arr,int left,int right);
int Partition(int *arr,int left,int right,int pivotindex);

int main()
{
    int a[20],n,ctr=0,j=0;
    printf("\nEnter number of elements:");
    scanf("%d",&n);
    printf("Enter array elements:");
    while(ctr<n)
    {
        scanf("%d ",&a[ctr]);
        ctr++;
    }
    Quick_sort(a,0,n-1);
    printf("\nSorted Array:");
    while(j<n)
    {
        printf("%d ",a[j]);
        j++;
    }
    return 0;
}

int Partition(int *arr,int left,int right,int pivotindex)
{
    int i,temp1,temp2,temp3,storeindex;
    storeindex=left;
    temp1=arr[pivotindex];        //value at pivot index

    //swap pivot with last element//
    arr[pivotindex]=arr[right];
    arr[right]=temp1;

    for(i=left;i<=right-1;i++)
    {
        if(arr[i]<=temp1)
        {
            temp2=arr[i];
            arr[i]=arr[storeindex];
            arr[storeindex]=temp2;
            storeindex++;
        }
    }

    //swap pivot with arr[storeindex] for its final place//
    temp3=arr[storeindex];
    arr[storeindex]=arr[right];
    arr[right]=temp3;

    return storeindex;
}

void Quick_sort(int *arr,int left,int right)
{
    int pivot,newpivot;
    if(right>left)
    {
        pivot=left+(right-left)/2;
        newpivot=Partition(arr,left,right,pivot);

    Quick_sort(arr,left,newpivot-1);
    Quick_sort(arr,newpivot+1,right);
    }

}

I am not getting any output on running the above code.. Though it compiles fine.. Any suggestion would be a great help! I am using codeblocks as the compiler.

[Narue]

I'm getting correct output for simple test cases. Perhaps you mean the output window is closing before you can see the results? If that's so, add a call to getchar just before returning from main:

int main()
{
    int a[20],n,ctr=0,j=0;
    printf("\nEnter number of elements:");
    scanf("%d",&n);
    printf("Enter array elements:");
    while(ctr<n)
    {
        scanf("%d ",&a[ctr]);
        ctr++;
    }
    Quick_sort(a,0,n-1);
    printf("\nSorted Array:");
    while(j<n)
    {
        printf("%d ",a[j]);
        j++;
    }
    getchar();
    return 0;
}

[gaurav_13191]

No that is not the problem.. The output window stays even after entering the input but there's no output.. Maybe there's some other error.. Which compiler did you use?

[vinitmittal2008]

@ gaurav
I am also using CODEBLOCKS and i compiled your program and its working fine. its showing sorted output after inputting desired values..

[Narue]

Alright then, since this is clearly reliant on input, please post some sample inputs that fail to produce output. This is a stupid question, but you are entering input such that the first loop terminates, right?

>Which compiler did you use?
Visual Studio 2010 and Pelles C.

[gaurav_13191]

It means there's some problem with my codeblocks.. thanks for all replies and it would help me if anyone can provide link on some tutorial to use codeblocks..

[Narue]

>It means there's some problem with my codeblocks
Why do people always assume it's the compiler? 99.9% of the time the problem is with your code, or your assumptions.

[vinitmittal2008]

scanf("%d ",&a[ctr]);

Remove space after %d its causing problem

scanf("%d",&a[ctr]);

[gaurav_13191]

Well thanks all.. Yes, I realize it was me making a minor mistake and finding faults in codeblocks. But that happened because I spent a lot of time on this program and still was not able to get correct output.

[vinitmittal2008]

>>>if anyone can provide link on some tutorial to use codeblocks..

http://www.codeblocks.org/docs/manual_en.pdf