Thread: quicksort program crashes without error

I'm trying to create a QuickSort algorithm but while I did have success in writing one that doesn't give me an error, the programm crashes after entering the unsorted numbers.

I already searched but couldn't find anything, could someone help me?

Code:

void swap(int left, int right, int Numbers[]) {
    int temp = Numbers[left];
    Numbers[left] = Numbers[right];
    Numbers[right] = temp;
    return;
}
 
void quicksort(int Beginning, int End, int Numbers[]) {
    int pivot = Numbers[((Beginning+1)+End)/2];
    int left = Beginning-1;
    int right = End;
    do {
 
        while (Numbers[left] < pivot) {
            left++;
        }
        while (Numbers[right] < pivot) {
            right--;
        }
 
        if (right > left) {
            swap(left,right,Numbers);
            left++;
            right--;
        }
    } while (left <= right);
    if (Beginning < right) {
        quicksort(Beginning,right,Numbers);
    }
    if (End < left) {
        quicksort(End,left,Numbers);
    }
}
 
int main()
{
    int End,Beginning,Dim,i;
    printf("Number of Elements: ");
    scanf("%d",&Dim);
    int Numbers[Dim];
    for ( i = 0 ; i < Dim ; i++ ) {
        printf("Enter the %d. element: ",i+1);
        scanf("%d",&Numbers[i]);
    }
    Beginning = 0;
    End = Dim-1;
    quicksort(Beginning,End,Numbers);
    printf("\ngsorted:");
    for ( i = 0 ; i < Dim ; i++ ) {
        printf("[%d]: %d",i+1,Numbers[i]);
    }
    return 0;
}

Originally Posted by stahta01

Why do you think this is correct?

Code:

int left = Beginning-1;

Tim S.

Well, because I learned that you can declare a variable while setting a value on it and Beginning-1 should be 1 subtracted from the variable Beginning. Is it wrong?

Well seems like I found the first mistake. Thanks for that, I tried another way before (Beginning was set to 1) but then changed my mind to this way and forgot to remove the -1. Well, now I just have to find out why it's stuck in an endless loop

Thanks I finally fixed all the errors.