void sort_by_area(triangle *tr, int n) {
// Sort an array a of the length n
    int *p=malloc(n*sizeof(int)); 
//create array of size n to store "volumes"
    for(int i=0;i<n;i++)
    {
	float a=(tr[i].a+tr[i].b+tr[i].c)/2.0;
//use 2.0 compulsary int/int gives int, int/float gives float
       p[i]=(a*(a-tr[i].a)*(a-tr[i].b)*(a-tr[i].c));
//formula without sqrt as areas are different guarenteed 
//because sqrt dosent work well with float values
    }
//bubble sort
    for(int i=0;i<n;i++)    
    {
        for(int j=0;j<n-i-1;j++)
        {
            if(p[j]>p[j+1])     
            {
                int temp=p[j];
                p[j]=p[j+1];
                p[j+1]=temp;
//swapping array of areas in ascending
//and simuntaneously the structure contents
                temp=tr[j].a;
                tr[j].a=tr[j+1].a;
                tr[j+1].a=temp;
                temp=tr[j].b;
                tr[j].b=tr[j+1].b;
                tr[j+1].b=temp;
                temp=tr[j].c;
                tr[j].c=tr[j+1].c;
                tr[j+1].c=temp;
            }
        }
    }
}