SDE - Intern

You are given a string 'STR' of length 'N'. You need to return a string that will contain all the characters present at the prime indices of the original string. The relative order of characters in the new string should be exactly the same as it was in the original string.

Note:

1. Prime indices are those indices that are prime numbers i.e. all the numbers except 0 and 1 which are divisible by 1 and the number itself. For eg. If a character is at index 5 in some string, then it is at a prime index, as 5 is a prime number.

2. The given string may consist of characters ‘a’-’z’, ‘A’-’Z’, ‘0’-’9’ at any place.

3. The given string follows 0-based indexing. So, assume that the first character of the given string is at index 0.

You have been given two Strings “STR1” and “STR2” of characters. Your task is to find the length of the longest common subsequence.

A String ‘a’ is a subsequence of a String ‘b’ if ‘a’ can be obtained from ‘b’ by deletion of several (possibly, zero or all) characters. A common subsequence of two Strings is a subsequence that is common to both Strings.

Ben Tennyson recently joined Coding Ninjas to become better at competitive programming.

To check whether Ben is seriously studying in Coding Ninjas or not, Gwen challenged Ben to solve a problem and Ben accepts the challenge of Gwen.

Gwen gives Ben an undirected graph of ‘N’ nodes numbered from 0 to ‘N - 1’ having ‘M’ edges. The task of Ben is to check whether the graph given by Gwen is a tree or not.

As Ben is busy fighting with Evil doers so he asked you to solve this problem.

Note :

There are no parallel edges and self-loops in the graph given by Gwen.

A tree is a connected graph having no cycles.