SDE - 2

You have been given an array/list ‘arr’ of length ‘N’, which contains single digit elements at every index. Your task is to return the sum of all elements of the array. But the final sum should also be a single digit.

To keep the output single digit - you need to keep adding the digits of the output number till a single digit is left.

For example:

For the given array [5, 8, 4, 9]

The sum of the elements of the array will be
5 + 8 + 4 + 9 = 26.
Since 26 is not a single-digit number, we will again take the sum of the digits of 26. 
2 + 6 = 8.
Now 8 is a single-digit number. So we will stop here and return 8.

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. 

Stack is a data structure that follows the LIFO (Last in First out) principle. Design and implement a stack to implement the following functions:

1. Push(num): Push the given number in the stack if the stack is not full.

2. Pop: Remove and print the top element from the stack if present, else print -1.

3. Top: Print the top element of the stack if present, else print -1.

4. isEmpty: Print 1 if the stack is empty, else print 0.

5. isFull: Print 1 if the stack is full, else print 0.

You have been given ‘m’ operations which you need to perform in the stack. Your task is to implement all the functions of the stack.

Example:

We perform the following operations on an empty stack which has capacity 2:

When operation 1 1 is performed, we insert 1 in the stack.

When operation 1 2  is performed, we insert 2 in the stack. 

When operation 2 is performed, we remove the top element from the stack and print 2.

When operation 3 is performed, we print the top element of the stack, i.e., 3.

When operation 4 is performed, we print 0 because the stack is not empty.

When operation 5 is performed, we print 0 because the stack is size 1, which is not equal to its capacity.

Design a chat application for a large company with thousands of employees.

Implement a Queue Data Structure specifically to store integer data using a Singly Linked List or an array.

You need to implement the following public functions :

1. Constructor: It initializes the data members as required.

2. enqueue(data): This function should take one argument of type integer. It enqueues the element into the queue.

3. dequeue(): It dequeues/removes the element from the front of the queue and in turn, returns the element being dequeued or removed. In case the queue is empty, it returns -1.

4. front(): It returns the element being kept at the front of the queue. In case the queue is empty, it returns -1.

5. isEmpty(): It returns a boolean value indicating whether the queue is empty or not.

Operations Performed on the Queue :

Query-1(Denoted by an integer 1): Enqueues integer data to the queue.

Query-2(Denoted by an integer 2): Dequeues the data kept at the front of the queue and returns it to the caller, return -1 if no element is present in the queue.

Query-3(Denoted by an integer 3): Fetches and returns the data being kept at the front of the queue but doesn't remove it, unlike the dequeue function, return -1 if no element is present in the queue.

Query-4(Denoted by an integer 4): Returns a boolean value denoting whether the queue is empty or not.

Given a singly linked list of integers. Your task is to return the head of the reversed linked list.

For example:

The given linked list is 1 -> 2 -> 3 -> 4-> NULL. Then the reverse linked list is 4 -> 3 -> 2 -> 1 -> NULL and the head of the reversed linked list will be 4.

Follow Up :

Can you solve this problem in O(N) time and O(1) space complexity?

1. Where do you see yourself in 5 years?