SDE - 1

Given a linked list having two pointers in each node. The first one points to the next node of the list, however, the other pointer is random and can point to any node of the list or null. The task is to create a deep copy of the given linked list and return its head. We will validate whether the linked list is a copy of the original linked list or not.

A deep copy of a Linked List means we do not copy the references of the nodes of the original Linked List rather for each node in the original Linked List, a new node is created.

For example,

Random pointers are shown in red and next pointers in black.

Implement a queue data structure which follows FIFO(First In First Out) property, using only the instances of the stack data structure.

Note:

1. To implement means you need to complete some predefined functions, which are supported by a normal queue such that it can efficiently handle the given input queries which are defined below.


2. The implemented queue must support the following operations of a normal queue: 

a. enQueue(data) : This function should take one argument of type integer and place the integer to the back of the queue.

b. deQueue(): This function should remove an integer from the front of the queue and also return that integer. If the queue is empty, it should return -1.

c. peek(): This function returns the element present in the front of the queue. If the queue is empty, it should return -1.

d. isEmpty(): This function should return true if the queue is empty and false otherwise.


3. You will be given q queries of 4 types:

a. 1 val - For this type of query, you need to insert the integer val to the back of the queue.

b. 2 - For this type of query, you need to remove the element from the front of the queue, and also return it.

c. 3 - For this type of query, you need to return the element present at the front of the queue(No need to remove it from the queue).

d. 4 - For this type of query, you need to return true if the queue is empty and false otherwise.


4. For every query of type:

a. 1, you do not need to return anything.

b. 2, return the integer being deQueued from the queue.

c. 3, return the integer present in the front of the queue.

d. 4, return “true” if the queue is empty, “false” otherwise.

Example

Operations: 
1 5
1 10
2
3
4

Enqueue operation 1 5: We insert 5 at the back of the queue.
Queue: [5]

Enqueue operation 1 10: We insert 10 at the back of the queue.
Queue: [5, 10]

Dequeue operation 2: We remove the element from the front of the queue, which is 5, and print it.
Output: 5
Queue: [10]

Peek operation 3: We return the element present at the front of the queue, which is 10, without removing it.
Output: 10
Queue: [10]

IsEmpty operation 4: We check if the queue is empty.
Output: False
Queue: [10]

You have been given stock values/prices for N number of days. Every i-th day signifies the price of a stock on that day. Your task is to find the maximum profit which you can make by buying and selling the stocks.

 Note :

You may make as many transactions as you want but can not have more than one transaction at a time i.e, if you have the stock, you need to sell it first, and then only you can buy it again.