SDE - 1

You have been given a string ‘ST’ of length ‘N’ and ‘X’ words all containing lowercase alphabets. You call a word matching from ‘ST’ if by removing some characters of ‘ST’ you can form that word.

Your task is to return the largest matching word among these ‘X’ words. If there are multiple strings of largest length return lexicographically smallest string. If no word matches from ‘ST’ return ‘#’ as the string.

Example:

Let’s say you have “abcd” as string ‘ST’ and 2 words “bd” and “db”. “bd” matches with the string ‘ST’ as you can remove ‘a’ and ‘c’ character to form “bd”. “db” does not match with the string ‘ST’ because it is impossible to form “db” from the string ‘ST’ by removing characters.

Note:

You cannot change the order of characters in ‘ST’ after removing some characters. 

You are given a Singly Linked List of integers. You have to find if the given linked list is circular or not.

A circular linked list is a sequence of elements in which every element has a link to its next element in the sequence and the last element has a link to the first element. This means that circular linked list is similar to the single linked list except that the last node points to the first node in the list.

While learning DSA, Ninja found two N-ary trees and wants to check whether they are mirror images of each other or not. But, he can’t find a suitable method to check the same. Can you help Ninja to solve this problem?

You are given two N-ary trees, ‘TREEA’ and ‘TREEB’ having ‘N’ vertices labeled from 0 to ‘N’-1, and both the trees are rooted at node 0. Your task is to find whether the trees are mirror images of each other or not. Edges of the tree are in order from left to right.

For Example:

For the given example below, the trees are mirror images of each other.

Ninja has been given a string ‘STR’ containing ‘(‘ and ‘)’. ‘STR’ may also contain lower case alphabets. In order to make ‘STR’ valid Ninja can remove either ‘)’ or ‘(’ from ‘STR’.

Here are some examples of valid ‘STR’ “((a))”, “(g)()”, “(())()”, "" (an empty string is also a valid string).

Ninja wants to know all the possible valid strings that can be formed from ‘STR’ by minimum possible removals (possibly zero).

Can you help Ninja to generate all valid strings from ‘STR’ by minimum removals?

For Example :

For the given ‘STR’ =  “()(()”, we can form a valid string “()()” by removing ‘(‘ at index 2 or 3.

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. 

What is demand paging? 
What is Semaphores and Deadlocks etc.