Data Structure

Question 1

to what DB the questions of Strings is similar to?

Answer 1

Arrays

Question 2

How does hash map works?

Answer 2

check

Question 3

what is the problem in hash map?

Answer 3

number of collision is very high

Question 4

worst case runtime of hash map?

Answer 4

O(N) n is the number of keys, but good implementation keeps collision to minimum the run time is O(1)

Question 5

how to implement hash table with balanced binary search tree?

Answer 5

IDK

Question 6

what is an array list? and what is it’s access run time?

Answer 6

it’s an array that resize itself as needed while providing O(1) access

Question 7

what is the run time of resizing the array list?

Answer 7

O(N) n is the number of items in the array list, but it happens so rarely, we can say that the insertion time is O(1)

Question 8

why the run time of insertion in array list is O(1)

Answer 8

IDK

Question 9

what is a linked list?

Answer 9

it’s a data structure that represent a sequence of nodes.

Question 10

linked list vs array?

Answer 10

IDK

Question 11

How to implement a linked list?

Answer 11

IDK

Question 12

what is the difference between looping while(n.next != null), while(n!= null), or while(n.next.next != null).
where n is the current node.

Answer 12

IDK

Question 13

what is the difference between singly and doubly linked list?

Answer 13

IDK

Question 14

what is the runner technique in Linked lists?

Answer 14

it’s a second pointer technique.
means iterate through the linked list with two pointers simultaneously.

Question 15

linked list and recursion.

Answer 15

IDK

Question 16

what operations does stack uses?

Answer 16

pop() remove the top item from the stack
push(item) add an item to the top of the stack
peek(): return the top of the stack
isEmpty() return true if and only if the stack is empty

Question 17

sum all the cons and pros of all data structures in table.

Answer 17

++++++++++++++++++++++++++_+

Question 18

what operations does a queue uses?

Answer 18

add(item): add an item to the end of the list
remove(): remove the first item in the list
peek() return the top of the queue
isEmpty() return true if and only if the queue is empty

Question 19

where do we often use queues?

Answer 19

in BFS or implementing a cache.

Question 20

what the heap is used for? and what it’s operation and complexity time?

Answer 20

Heaps are commonly used to implement priority queues
insertion: O(log N) where ‘N’ is the number of elements. insert it at the end then rearrange the heap
deletion O(log N) delete then rearrange the heap.
peek: O(1) peek the root