What is the mistake?

#1
#2

Your code is not working in case of worst case as, For eg, when ur array is completely reversed…
Then The complexity of quicksort will be O(n^2)… So to consider that test case… You need to create a shuffle function… so that you get a random array and then u can simply apply quicksort function to the newly random array obtained…

void shuffle(ll *a,ll s,ll e)
{
ll j;
srand(time(NULL));
for(ll i=e;i>0;i–)
{
j=rand()%(i+1);
swap(a[i],a[j]);
}
}