SDE - 1

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.

You have been given a Binary Tree of integers. You are supposed to return the reverse of the level order traversal.

For example:

For the given binary tree

The reverse level order traversal will be {7,6,5,4,3,2,1}.

Given a singly linked list of 'N' nodes. The objective is to determine the middle node of a singly linked list. However, if the list has an even number of nodes, we return the second middle node.

Note:

1. If the list is empty, the function immediately returns None because there is no middle node to find.
2. If the list has only one node, then the only node in the list is trivially the middle node, and the function returns that node.

Design and implement a data structure for Least Recently Used (LRU) cache to support the following operations:

1. get(key) - Return the value of the key if the key exists in the cache, otherwise return -1.

2. put(key, value), Insert the value in the cache if the key is not already present or update the value of the given key if the key is already present. When the cache reaches its capacity, it should invalidate the least recently used item before inserting the new item.

You will be given ‘Q’ queries. Each query will belong to one of these two types:

Type 0: for get(key) operation.
Type 1: for put(key, value) operation.

Note :

1. The cache is initialized with a capacity (the maximum number of unique keys it can hold at a time).

2. Access to an item or key is defined as a get or a put operation on the key. The least recently used key is the one with the oldest access time.

You are given an array “A” of N integers. Your task is to find the maximum element in all K sized contiguous subarrays from left to right.

For Example:

If A = [3, 2, 3], and K = 2.
Then max of [3, 2] = 3 and max of [2, 3] = 3
So, the answer will be [3, 3]

If A = [3, 2, 3, 5, 1, 7] and K = 3.
Then max of [3, 2, 3] = 3 
Then max of [2, 3, 5] = 5 
Then max of [3, 5, 1] = 5 
Then max of [5, 1, 7] = 7 
So  the answer will be [3, 5, 5, 7]

Follow Up :

Can you solve the problem in O(N) time complexity and O(K) space complexity?