Add DP problems

[Geetanjaligupta123]

I want to add DP Problems with solutions in C++ Can you please assign this issue to me.

[hydrodog]

Since this is a course, creating a great problem in C++, with a main specified would be great. However, please do not post the solution or I can't ask students to solve it. You can email me a solution privately!

The most important thing about a high quality problem is going to be the clearly stated comment inside explaining what the student is supposed to do, or a markdown document describing the problem.

Feel free to create a directory dp, dpproblems.md with a description of the problems, and each problem with a main. Then do a pull request and I will be happy to accept if it fits the needs of the course.