What is the space complexity of this code?

Question

int f(int n)
{ 
    if (n <= 1)
    { 
         return 1;
    } 
    return f(n - 1) + f(n - 1);
} 

I know that the time complexity is O(2

Answer 1

Space complexity is O(n) because one side of recursion, reaches the leaves, and returns up, until the root, similar happens for the other side of recursion and in every middle step, the space used in the recursion cannot be bigger than O of depth of recursion tree.