2.3.2 - Algorithms for Main Data Structures

Question 1

What is a stack?

Answer 1

A stack is a first-in, last-out data structure.

Question 2

How do you check the size of a stack?

Answer 2

Size()

Question 3

How do you check if a stack is empty?

Answer 3

isEmpty()

Question 4

How do you return the top element of a stack but not remove it?

Answer 4

Peek()

Question 5

How do you add an item onto a stack?

Answer 5

Push(element)

Question 6

How do you return and remove the top element of a stack?

Answer 6

Pop()

Question 7

What is a queue?

Answer 7

A queue is a first-in, first-out data structure.

Question 8

How do you check the size of a queue?

Answer 8

Size()

Question 9

How do you check if the queue is empty?

Answer 9

IsEmpty()

Question 10

How do you return the front element but not remove it from a queue?

Answer 10

Peek()

Question 11

How do you add an element to a queue?

Answer 11

Enqueue(element)

Question 12

How do you remove and return the front element from a queue?

Answer 12

Dequeue()

Question 13

How is a tree formed?

Answer 13

Trees are formed from nodes and edges.

Question 14

What are the two types of tree-traversal?

Answer 14

Depth first (post-order) traversal and breadth first traversal.

Question 15

How does depth first traversal work?

Answer 15

It works in the same way as a post-order traversal.

Draw around the graph and mark the nodes when the drawing goes around on the right of the node.

Question 16

How does breadth first traversal work?

Answer 16

It works by visiting all of the children of the start node and then all nodes directly connected to them.

In simple terms, go across from the top left to the bottom right.

Question 17

What is a binary search tree?

Answer 17

A tree where each node can have a maximum of two child nodes.

The left child node is alphabetically or numerically lower than the parent node and the right child node is alphabetically or numerically higher than the parent node.

Question 18

How is a node deleted from a tree?

Answer 18

1) The tree is searched to find the node to be deleted.
2) Replace the content of the node to be deleted to null.
3) Make the parent node point to the child node of the node to be deleted.
4) Add the node to be deleted to the empty node list.

Question 19

How is a node added to a tree?

Answer 19

1) Search the tree to find the value where the node needs to be added to.
2) Create a new node with the correct value.
3) Add a pointer from the parent node to the new node.
4) Make the new node point to null.

Question 20

What are similarities between a tree and a graph?

Answer 20

Both consist of nodes.

Both are connected by edges/links.

Both are dynamic data structures.

Question 21

What are differences between a tree and a graph?

Answer 21

Tree is 1-directional whereas a graph is 2-directional.

Tree has a root node whereas a graph doesn’t have a clear root node.

Trees are not weighted whereas graphs can be.

Trees will not have cycles whereas graphs can contain cycles.

Question 22

What are differences between recursion and iteration?

Answer 22

Recursion uses more memory than iteration.

Recursion can run out of memory whereas iteration cannot.

Recursion will call itself whereas iteration does not.

Question 23

What are four features in an IDE that help with debugging?

Answer 23

Stepping through the code to run one line at a time.

Syntax error highlighting.

Breakpoints.

Variable watch window.

Question 24

How does stepping through the code help with debugging?

Answer 24

Runs one line at a time to see where the error is.

Question 25

How does syntax error highlighting help to debug a program?

Answer 25

To distinguish syntax errors in the program code.

Question 26

How does setting breakpoints help with debugging?

Answer 26

It allows individual sections of code to be debugged at one time.

Question 27

How does a variable watch window help with debugging?

Answer 27

It checks that the variables are being updated correctly.