Question

Recurrence relation - how to find it for a function?

Assume that n is the number of elements of A[first, . . . , last], that is, n = last −
first + 1.
Algorithm jelly(A, first, last)
if (n < 8) then
return A[first] + A[last]
third ← (2 * first + last) / 3
return jelly(A, first + 3, last - 2) * jelly(A, first, third)

Answer 1

If you mean recurrence as in recursion then you need to think of both the n-1 and base case. I would suggest trying to think of what the base case is and then the next case etc. If you cannot do this then the problem cannot be solved by recursion.