Problem with running code for TSORT

help
,
1

I’m facing problems running my C code for the problem TSORT.
Whenever I run the code given below it shows SIGSEGV error. I am unable to understand why I am facing this error.

#include <stdio.h>

void swap(int a, int b){
    a = a + b;
    b = a - b;
    a = a - b;
}


int partition(int arr[], int low, int high){
    int i, j;
    i = low - 1;
    for (j = low; j < high; j++){
        if (arr[j] < arr[high]){
            i++;
            swap(arr[i], arr[j]);
        } 
    }
    swap(arr[i + 1], arr[high]);
    return (i + 1);
}

void quicksort(int arr[], int low, int high){
    int pivot;
    pivot = partition(arr, low, high);
    quicksort(arr, low, pivot-1);
    quicksort(arr, pivot+1, high);
}


main(){
    int n, i;
    scanf("%d", &n);
    int arr[n];
    for (i = 0; i < n; i++)
        scanf("%d", &arr[i]);
    quicksort(arr[n], 0, n-1);
    for (i = 0; i < n; i++){
        printf("%d\n", arr[i]);
    }
}
2

Honking great compiler error when compiling with C++, which has stricter type-safety than C:

rishab_04-TSORT.cpp: In function ‘int main()’:
rishab_04-TSORT.cpp:37:20: error: invalid conversion from ‘int’ to ‘int*’ [-fpermissive]
     quicksort(arr[n], 0, n-1);
               ~~~~~^

Edit:

Also, your swap is a no-op.

Edit2:

Also - quicksort - which is called recursively - doesn’t seem to have a base case/ stop condition.

3

@rishab_04 Try My Answer
https://www.codechef.com/viewsolution/44803712
Its In Java, You Can Grasp The Concept And Try To Rewrite It In C

4

Thank you for the reply, just a few concerns here:
I don’t understand why would there be any type conversion when I’m passing an integer array to a function which is supposed to accept integer arrays.
That swap code was something I used extensively in integer swaps while practising Java, so I just used it here without much thought. Is it a bad programming practice?

5

That’s not what you’re doing here:

 quicksort(arr[n], 0, n-1);

arr[n] is an integer, not an integer array (and you’re also making an out-of-bounds access).

Writing a swap function that doesn’t actually do anything is “a bad programming practice”, yes :wink:

Have you actually tried it?

#include <stdio.h>
  
void swap(int a, int b){
    a = a + b;
    b = a - b;
    a = a - b;
}


int main(){
    int x = 3, y = 4;
    swap(x,y);
    printf("x: %d y: %d\n", x, y);
}