General Data Structures

Question 1

What is the toString() method?

Answer 1

A special method that returns a string representation of an object

Question 2

How to use the toString() method in our classes?

Answer 2

public String toString(){
return constructor1 + “ “ + data1;

}

Must include the method toString to our class object and edit how we want it to act

Include an @Override before the method

Question 3

Why do we use toString()?

Answer 3

So we can print out an object in the form of a string rather than the address of the object

Question 4

What is an Array?

Answer 4

A fixed size that stores elements in a linear set

Question 5

What is a Dynamic Array? Array Lists

Answer 5

Resizeable Array

Question 6

What is a linked list?

Answer 6

Nodes linked via pointers

Question 7

What is a Stack?

Answer 7

LIFO, think of a stack of books

Question 8

What is deque? queue

Answer 8

Double-ended queue

Question 8

What is a Queue?

Answer 8

FIFO, think of a line

Question 9

What is a Hash Table?

Answer 9

Stores key-value pairs

Question 10

What is a Hash Set?

Answer 10

Unordered set, unique elements

Question 11

What is a Binary Tree?

Answer 11

Each node has ≤2 children

Question 12

What is a Binary Search Tree BST?

Answer 12

Ordered binary tree

Question 13

What is an AVL Tree?

Answer 13

Self-balancing BST

Question 14

What is a Red-Black tree?

Answer 14

Balanced BST used in TreeSet, TreeMap

Question 15

What is a Segment Tree?

Answer 15

Used for range queries

Question 16

What is a Fenwick Tree?

Answer 16

Efficient prefix sum computation

Question 17

What is a Trie?

Answer 17

Used for string prefix searches

Question 18

What is a Min Heap?

Answer 18

Smallest element at the root

Question 19

What is a Max Heap?

Answer 19

Largest element at the root

Question 20

What is a priority Queue?

Answer 20

Supports Efficient Retrieval of min/max

Question 21

What is an Adjacency Matrix?

Answer 21

Graphs as a 2D Array

Question 22

What is an Adjacency List?

Answer 22

Graph as a list of lists

Question 23

How to implement basic Array?

Answer 23

int[] array = new int[10];

Question 24

How to implement an Array List?

Answer 24

List arrayList = new ArrayList<>();

Question 25

How to implement a Linked List?

Answer 25

LinkedList linkedList = new LinkedList<>();

Question 26

How to implement a Stack?

Answer 26

Stack stack = new Stack<>();

Question 27

How to implement a Queue?

Answer 27

Queue queue = new LinkedList<>();

Question 28

How to implement a Deque?

Answer 28

Deque deque = new ArrayDeque<>();

Question 29

How to implement a HashMap?

Answer 29

Map hashMap = new HashMap<>();

Question 30

How to implement a HashSet?

Answer 30

Set hashSet = new HashSet<>();

Question 31

How to implement a LinkedHashMap?

Answer 31

Map linkedHashMap = new LinkedHashMap<>();

Question 32

How to implement a LinkedHashSet?

Answer 32

Set linkedHashSet = new LinkedHashSet<>();

Question 33

How to implement a TreeSet?

Answer 33

TreeSet treeSet = new TreeSet<>();

Question 34

How to implement a TreeMap?

Answer 34

TreeMap treeMap = new TreeMap<>();

Question 35

How to implement a Min Heap?

Answer 35

PriorityQueue minHeap = new PriorityQueue<>();

Question 36

How to implement a Max Heap?

Answer 36

PriorityQueue maxHeap = new PriorityQueue<>(Collections.reverseOrder());

Question 37

How to implement a Adjacency List?

Answer 37

Map> graph = new HashMap<>();

Question 38

How to implement a Adjacency Matrix?

Answer 38

int[][] adjMatrix = new int[10][10];