121 Week 9 - Recursion

Question 1

Iteration and recursion

Answer 1

Used to traverse a set of values or run the same logic a given number of times.
Any recursive solution can be written in an iterative way.
Any iterative solution can be written in a recursive way.

Question 2

Iteration

Answer 2

A function which uses loops to execute the same logic multiple times.

Question 3

Recursion

Answer 3

A function which calls itself to execute the same logic multiple times.

Question 4

Order of execution in recursion.

Answer 4

The order in which logic is executed in recursion depends on if the logic is before or after the function calls itself.

Question 5

Single recursion

Answer 5

A recursive function where you only need to have one self-call for each function call.
It is generally easy to write iteratively.

Question 6

Multiple recursion

Answer 6

A recursive function where you need to have more than one self-call for each function call.
It is generally harder to write iteratively because we need to explicitly track state.

Question 7

Reasons to use iteration

Answer 7

Memory usage is controlled explicitly by the programmer, so a “stack overflow“ less likely.
Can executes more quickly, as there is no overhead from stack frame creation / destruction.
Iterative functions can be easier to understand than a recursive function.

Question 8

Reasons to use recursion

Answer 8

Recursive functions are much more concise than iterative functions.
Languages which support tail recursion can eliminate some of the extra cost to performance, and stack overflows.