Adding hard leetcode problem approach & solution

[Devolious]

@MilindGupta-Creator I would like to add the approach and solution to one of the tough and concept-provoking leetcode questions Pizza with 3n slices (A non-conventional DP problem). Please assign it to me.

[Abhishek3223]

i would like to work on this

[satyamgupta461]

Hey @MilindGupta-Creator. I have quite a good hands-on knowledge of JAVA and I have done this Happy number code in JAVA. Please appoint me to the project.

[gauriimaheshwarii]

Hi @MilindGupta-Creator, this issue is now solved by the PR (#128).
Kindly merge.

[Devolious]

@MilindGupta-Creator I wish to add a classic binary search problem named Peak Index in a mountain. Please assign it to me.

[Abhishek-Anand25]

sir please assign this issue to me ?