Recursive / Lists

Question 1

What is a base case?

Answer 1

The most simplest form of the recursive problem. The condition that causes the method to end.

Question 2

What is the recursive case?

Answer 2

The steps that an algorithm takes to make the problem one step smaller and move towards the base case.

Question 3

What is recursion?

Answer 3

When a code calls itself in its code.

Question 4

What are data structures?

Answer 4

A combination of multiple values.

Question 5

What are linked lists?

Answer 5

A data structure that stores a sequence of elements.

Question 6

What are the parts of a linked list?

Answer 6

Each element is called a node.
The first node is called the head.
The last node is called the tail.

Question 7

What does each node have?

Answer 7

A value
A reference to the next node in the list

Question 8

first

Answer 8

Takes the first node of a list

Question 9

rest

Answer 9

Results in a list of everything but the head.

Question 10

How do you use build-list?

Answer 10

(build-list
number of elements in the list
function applied to each number)

Question 11

length

Answer 11

counts the number of elements

Question 12

list-ref

Answer 12

extract by position
(list-ref (list 1 2 3) 0) -> 1

Question 13

append

Answer 13

combines lists together from left to right

Question 14

reverse

Answer 14

puts a list in reverse order

Question 15

member

Answer 15

Checks a list for an element. Comes out #f if not found. If found, a list is created with every node after it in the list.

Question 16

How do you use filter?

Answer 16

(filter
function
list)

Question 17

What is foldl?

Answer 17

Applies a function to nodes from left to right

Question 18

How do you use foldl?

Answer 18

(foldl function start-value list)

Question 19

What is foldr?

Answer 19

Foldl but lists lists from right to left.

Question 20

How do you use map?

Answer 20

(map function list)

Question 21

map

Answer 21

A function used to apply a function to each element of one or more lists
Results in a list

Question 22

What does car do?

Answer 22

Returns the first item in a list
Error if the list is empty

Question 23

What does cdr do?

Answer 23

Returns a LIST of everything but the first node
Returns an error if the list is empty

Question 24

Do you do car or cdr first if you see them combined?

Answer 24

cdr

Question 25

How many cdr’s can you abbreviate together?

Answer 25

5

Question 26

What is a constructor?

Answer 26

Creates a new object, like a list object

Question 27

cons

Answer 27

means “construct”
returns a list of two arguments combined
puts the first argument as the head

Question 28

Difference between cons and built-list

Answer 28

built-list relies on a function.