Problems on Sliding Window Technique

[gnp31]

I am currently working on these sliding window technique problems:

1. Find the longest substring of given string containing k distinct characters
2. Longest substring of given string containing distinct characters
3. Find all substrings of a string that are permutation of a given string
4. Print all sub-arrays of an array having distinct elements
5. Find duplicates within given range k in an array

Shall I make a separate folder and push?

[gnp31]

I have made a PR.
Please check.