Anyone needs hash tables?

Hi, I’m (full name) and I’m quite delighted to say that I want to be a part of your “HacLabs” family. For quite sometime, I’ve been doing studies and courses on "Hash Table" concept.
Hash Table is a data structure which stores data in an associative manner. In a hash table, data is stored in an array format, where each data value has its own unique index value. Access of data becomes very fast if we know the index of the desired data.

I’ve done some minor projects in this concept like- “Sudoku Solver”, “Valid Sudoku”, “Set Mismatch” and many more small projects. Now, that I think I have grasped this concept, I want to explore it deeper by doing further research and implementing on practicals. Now, this is where I need your help in guiding me for tougher and exciting projects which can lead to lots of brain-storming. Projects like- “Grid Illumination”, “Get watched videos by your friends”, “Binary Tree in-order traversal” and so on.