Recursive Algorithm Question

Question

I am having a difficult time figuring out where to start this problem. Any input on where to start would be greatly appreciated.

Consider the recursive algorithm, which operates on a sequence of real numbers, S = {s0, s1, s2, ..., sn):

Function Questo(S)

First := the first element of s

If length(S) is 1

return First

End-if

S1 := S with the first element removed

return first + Questo(S1)

Let sequence T := (4,2,-1,3)

Which value is returned by Questo(T)?

Answer 1

\begin{align} \text{Questo}(T) &= \color{orange}{\text{Questo}(4,2,-1,3)} \\ &= 4 + \color{green}{\text{Questo}(2,-1,3)} \\ &= 4 + 2 + \color{blue}{\text{Questo}(-1,3)} \\ &= 4 + 2 + (-1) + \color{red}{\text{Questo}(3)} \\ &= 4 + 2 + (-1) + \color{red}{3} \\ &= 4 + 2 + \color{blue}{2} \\ &= 4 + \color{green}{4} \\ &= \color{orange}{8} \end{align}