Algorithm and Data Structures

Question 1

What is a data structure?

Answer 1

A data structure is a way of storing and organizing data according to a certain format or structure, allowing us to access and manipulate the data in a certain way

Question 2

Examples of data structures

Answer 2

tables to display schedules

a novel stores and organizes texts in paragraphs

Question 3

Why are data structures important?

Answer 3

Data structures are a crucial part of computer programming as programming relies on our ability to store data, access that data, and manipulate that data to create the desired outcome.

Therefore, it is a top priority that engineers leverage data structures optimally to organize and manipulate data in an efficient and meaningful way

Question 4

What are the 4 primary data structures in Python3?

Answer 4

1. List
2. Tuple
3. Dictionary
4. Set

Question 5

So when thinking about a program… the data structure should be top of mind in the process of mapping out the path to success

Answer 5

1. What are we trying to achieve?
2. What data will we need?
3. What data do we have already?
4. What will we need to do with the data?
5. What are our challenges?
6. How is this data stored?
7. How will we interact with the data?
8. How will we store the data?
9. How will we access the data?
10. How will we manipulate the data to create our desired outcome?
11. How will we overcome our challenges?

what are the conditions needed to produce an optimal output from the given input?

Question 6

What is a list?

Answer 6

a data structure that allows us to store elements of different data types in one container, linearly. Each element is indexed from 0 and up

Question 7

Are lists mutable?

Answer 7

Yes, lists are mutable.

Question 8

Are lists ordered?

Answer 8

Yes, lists are ordered linearly with each element at a specific index. The first element is at index 0, the next is at index 1, and so forth

Question 9

What are two ways to merge two lists together?

Answer 9

1. using the + operator

merged_list = list_1 + list_2

2. using the extend() property of a list to add the elements of one list at the end of another:

merged_list = list_1.extend(list_2)

Question 10

two ways of adding elements to a list

Answer 10

1. the append() method adds an element to the end of a list
   list. append(new_element)
2. the insert() method adds an element at a specified index within a list
   list. insert(1, new_element)

Question 11

two ways of removing an element from a list

Answer 11

1. the pop() method removes the last element from a list, and returns that element
   list. pop()
2. the remove() method removes a specified element from a list
   list. remove(this_element)

Question 12

what is list slicing?

Answer 12

provides a sublist of the list being sliced.

the syntax for list slicing is:

list[starting_index, ending_exclusive_index, steps]

Question 13

How can we verify the existence of an element in a list?

Answer 13

using the in operator

element_hello in list

this will return True if element_hello is in the list
and False if not in the list

Question 14

What is list comprehension?

Answer 14

a technique that uses a for loop to create a new list from an existing list

since the result is always a NEW list, it’s good practice to assign list comprehension to a new variable

list comprehension is enclosed in square brackets

Question 15

What is a tuple?

Answer 15

a tuple is similar to a list in that it can contain different data types and is ordered linearly and 0 indexed

a tuple is different because it is enclosed in parentheses AND is immutable. Meaning the tuple cannot be altered. BUT, the elements of a tuple are mutable and can be altered

since tuples are immutable, it is NOT possible to add or delete elements from an existing tuple

Question 16

What is a dictionary?

Answer 16

an unordered data structure that stores data as key-value pairs, where each unique key is an index which holds the value associated with it

key:value pairs are accessed in a random, unordered manner

Question 17

What is a set?

Answer 17

an unordered collection of data items

Question 18

When would I use a set?

Answer 18

when you need to keep track of the existence of items

a set doesn’t allow duplicates. So you can convert another data structure to a set to remove duplicates

Question 19

Set Theory Operations

Answer 19

are the operations of a set: union, intersection, difference

Question 20

What is a Union?

Answer 20

a collection of all unique elements from both sets

syntax is the pipe, ‘|’, operator or the union() method

Question 21

What is the intersection?

Answer 21

a collection of unique elements which are common between two sets

syntax is the ‘&’ operator or the intersection() method

Question 22

What is the difference?

Answer 22

a collection of all the unique elements present in the first set and not present in the second set

syntax: - operator, or difference() method

Question 23

Data Structure Conversion: Explicit Conversion

Answer 23

syntax: destination_structure_name(source_structure_object)

where destination structure is the data structure we want to convert to

and source_structure is the object we want to convert

Question 24

Converting to a list

Answer 24

we use the listt() constructore

when converting a dictionary to a list, only the keys will be converted to a list

Question 25

Converting to a Tuple

Answer 25

any data structure can be converted to a tuple using the tuple() constructor

In the case of converting a dictionary, only the keys will be converted to a tuple

Question 26

Converting to a Set

Answer 26

use the set() constructor to convert any data structure to a set

in the case of a dictionary, only the keys will be converted to a set

Question 27

converting to a dictionary

Answer 27

the dict() constructor can be used to a convert a tuple with a length of two to a dictionary, since it reuqires a pair of data to serve its key: value format

Question 28

What is the syntax for filter?

Answer 28

filter(function, iterable)

Question 29

What is a Stack? And When is it useful?

Answer 29

Imagine a stack of books

to build this stack of books we add the first book to the bottom, then the next book on top of the first, and so forth.

To retrieve a book from the stack, we remove a book from the top one by one until we retrieve the book we were seeking

Question 30

What are the Stack operations?

Answer 30

Push, Pop, Peek

Push: inserts an element onto a stack as the new last/top element of the stack

Pop: removes the top/last element from the stack

Peek: ask’s the Stack, ‘What is the top element?’

Question 31

What are the advantages of a Stack data structure?

Answer 31

…

Question 32

What are the advantages of a Stack data structure?

Answer 32

…

Question 33

What are the uses of stacks?

Answer 33

Compilers and Parsers leverage stacks

Activation records: use stacks to keep track of the procedure activities during runtime

Question 34

What are the uses of stacks?

Answer 34

Compilers and Parsers leverage stacks

Activation records: used to keep track of the procedure activities during runtime of a program. Activation record is a fundamental part of programming languages and is implemented using a stack. When the function is called, an activation record is created for it and keeps track of parameters, local variables, return address, static and dynamic links, and the return value.

Web Browsers: use a stack to keep track of URLs you have visited. When you visit a page it adds it to the top and the stack. When you hit the back button the stack is popped and the previous URL you visited is accessed

To implement other Data Structures: Stacks are used to implement searches in Graphs and Trees, which are other complex data structures.

Question 35

What are the different types of Linked Lists?

Answer 35

Singly
Doubly
Circular

Question 36

What are the tradeoffs between an Array and a Linked List?

Answer 36

Insertion/Deletion: since an array has contiguous memory, in an array, you have to shift all the other elements toward the end(insertion) or the beginning(deletion). This makes an array less efficient than a Linked List for this use case. The time complexity is O(n) for an array and O(1) for a linked list

Accessing: since an array has contiguous memory, accessing an element at a specific index is more efficient than accessing nth elements in a linked list.

Question 37

What is a linked list?

Answer 37

a linked list is a data structure made up of nodes. Each node has two components: 1) data 2) next

the data component allows the node to store data

the next component is a pointer that points its node to the next node

the start of the linked list is the head, which starts at the beginning of the linked list. To access and element in a linked list we always begin at the head and traverse the linked list from there.

the end of the linked list is what we call Null or None (in Python). The last node in the linked list points to a null object, and that tells you that its the end of the linked list