Frontend Developer Intern

You are given an array/list 'ARR' consisting of N integers, which contains elements only in the range 0 to N - 1. Some of the elements may be repeated in 'ARR'. Your task is to find all such duplicate elements.

Note:

1. All the elements are in the range 0 to N - 1.
2. The elements may not be in sorted order.
3. You can return the duplicate elements in any order.
4. If there are no duplicates present then return an empty array.

You are given a string 'STR'. The string contains [a-z] [A-Z] [0-9] [special characters]. You have to find the reverse of the string.

For example:

 If the given string is: STR = "abcde". You have to print the string "edcba".

follow up:

Try to solve the problem in O(1) space complexity. 

You must implement the Stack data structure using a Singly Linked List.

Create a class named 'Stack' which supports the following operations(all in O(1) time):

getSize: Returns an integer. Gets the current size of the stack

isEmpty: Returns a boolean. Gets whether the stack is empty

push: Returns nothing. Accepts an integer. Puts that integer at the top of the stack

pop: Returns nothing. Removes the top element of the stack. It does nothing if the stack is empty.

getTop: Returns an integer. Gets the top element of the stack. Returns -1 if the stack is empty