SDE - 1

You are given a string 'exp' which is a valid infix expression.

Convert the given infix expression to postfix expression.

Note:

Infix notation is a method of writing mathematical expressions in which operators are placed between operands. 

For example, "3 + 4" represents the addition of 3 and 4.

Postfix notation is a method of writing mathematical expressions in which operators are placed after the operands. 

For example, "3 4 +" represents the addition of 3 and 4.

Expression contains digits, lower case English letters, ‘(’, ‘)’, ‘+’, ‘-’, ‘*’, ‘/’, ‘^’. 

Example:

Input: exp = ‘3+4*8’

Output: 348*+

Explanation:
Here multiplication is performed first and then the addition operation. Hence postfix expression is  3 4 8 * +.

You are given a linked list of 'n' nodes and an integer 'k', where 'k' is less than or equal to 'n'.

Your task is to reverse the order of each group of 'k' consecutive nodes, if 'n' is not divisible by 'k', then the last group of nodes should remain unchanged.

For example, if the linked list is 1->2->3->4->5, and 'k' is 3, we have to reverse the first three elements, and leave the last two elements unchanged. Thus, the final linked list being 3->2->1->4->5.

Implement a function that performs this reversal, and returns the head of the modified linked list.

Example:

Input: 'list' = [1, 2, 3, 4], 'k' = 2

Output: 2 1 4 3

Explanation:
We have to reverse the given list 'k' at a time, which is 2 in this case. So we reverse the first 2 elements then the next 2 elements, giving us 2->1->4->3.

Note:

All the node values will be distinct.

You are given ‘n’ cities, some of which are connected by bidirectional roads. You are also given an ‘n x n’ matrix i.e. ‘roads’, where if city ‘i’ and ‘j’ are connected by a road then ‘roads[i][j]'= 1, otherwise ‘roads[i][j]' = 0.

A province is a group of cities that are either directly or indirectly connected to each other through roads.

The goal is to count and return the total number of such provinces in the given matrix.

Example:

n = 4, roads = [ [1, 1, 1, 0],
                 [1, 1, 1, 0],
                 [1, 1, 1, 0],
                 [0, 0, 0, 1] ]

So, there are ‘2’ provinces.

Note:

1. A city is connected to itself. So, for every city ‘i’, ‘roads[i][i] = 1’.

You have been given a long type array/list 'arr’ of size 'n’.

It represents an elevation map wherein 'arr[i]’ denotes the elevation of the 'ith' bar.

Print the total amount of rainwater that can be trapped in these elevations.

Note :

The width of each bar is the same and is equal to 1.

Example:

Input: ‘n’ = 6, ‘arr’ = [3, 0, 0, 2, 0, 4].

Output: 10

Explanation: Refer to the image for better comprehension:

Note :

You don't need to print anything. It has already been taken care of. Just implement the given function.

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.

Explain Banker’s algorithm with an example, Thrashing, Deadlock, Semaphore, etc

ACID properties, Memory management

For a given array with N elements, you need to find the length of the longest subsequence from the array such that all the elements of the subsequence are sorted in strictly increasing order.

Strictly Increasing Sequence is when each term in the sequence is larger than the preceding term.

For example:

[1, 2, 3, 4] is a strictly increasing array, while [2, 1, 4, 3] is not.