Epihany. having a separate function for calculating area makes the code much simpler to understand and implement...

float calcArea (triangle tr) //func for cleaner code to calculate the area

{ float p = (tr.a + tr.b + tr.c) / 2.0;

return sqrt (p * (p - tr.a) * (p - tr.b) * (p - tr.c));

}

void sort_by_area(triangle* tr, int n)

{

for (int i = 0; i < n - 1; i++)

{

    for (int j = 0; j - n - 1; j++)

    {

        if(calcArea(tr[j]) > calcArea(tr[j+1]))

        {

            triangle temp = tr[j];

            tr[j] = tr[j+1];

            tr[j+1] = temp;

        }

    }

}

}

This is also one of the same way double area(triangle tr) { double s=(tr->a+tr->b+tr->c)/2.0; if((tr->a+tr->b)>tr->c&&(tr->b+tr->c)>tr->a&&(tr->a+tr->c)>tr->b) { double area=sqrt(s(s-tr->a)(s-tr->b)(s-tr->c)); return area;

}
return 0;

}

void sort_by_area(triangle* tr, int n) {

double arr[n];
for(int i=0;i<n;i++)
{
     arr[i]=area(&tr[i]);
}
for(int i=0;i<n;i++)
{
    for(int j=0;j<i;j++)
    {
        if (j == i)
        {
          arr[j] = arr[i]; 
        }
        if(arr[j]>arr[i])
        {
            double temp_1=arr[j];
            arr[j]=arr[i];
            arr[i]=temp_1;
            triangle temp=tr[j];
            tr[j]=tr[i];
            tr[i]=temp;
        }
    }

}

}

1. double calculate_area(triangle tr) {
2. double s = (tr.a + tr.b + tr.c) / 2.0;
3. return sqrt(s * (s - tr.a) * (s - tr.b) * (s - tr.c));
4. }
5. 6. int compare(const void *a, const void *b) {
6. triangle *tr1 = (triangle *)a;
7. triangle *tr2 = (triangle *)b;
8. double area1 = calculate_area(*tr1);
9. double area2 = calculate_area(*tr2);
10. if (area1 < area2) return -1;
11. if (area1 > area2) return 1;
12. return 0;
13. }
14. 16. void sort_by_area(triangle* tr, int n) {
15. /**
    • Sort an array a of the length n */
16. qsort(tr, n, sizeof(triangle), compare);

Why does my code compile differently in vscode than in the test case here?

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

struct triangle
{
	int a;
	int b;
	int c;
};

typedef struct triangle triangle;
double squart(triangle triangle)
{
    double p = (triangle.a + triangle.b + triangle.c) / 2.0;
    double s = sqrt((double)(p * (p - triangle.a) * (p - triangle.b) * (p - triangle.c)));
    return s;
}
void sort_by_area(triangle* tr, int n) {
	/**
	* Sort an array a of the length n
	*/
    int tap = n / 2;
    for(tap; tap > 0; tap /= 2)
    {
        for(int i = tap; i < n; i++)
        {
            for(int j = i - tap; j >= 0 && squart(tr[j]) > squart(tr[j+tap]); j -= tap)
            {   
                triangle temp = tr[j];
                tr[j] = tr[j+tap];
                tr[j+tap] = temp;
            }
        }
    }
}

int main()
{
	int n;
	scanf("%d", &n);
	triangle *tr = malloc(n * sizeof(triangle));
	for (int i = 0; i < n; i++) {
		scanf("%d%d%d", &tr[i].a, &tr[i].b, &tr[i].c);
	}
	sort_by_area(tr, n);
	for (int i = 0; i < n; i++) {
		printf("%d %d %d\n", tr[i].a, tr[i].b, tr[i].c);
        // printf(" s = %.2lf", squart(tr[i]));
	}
	return 0;
}