Algorithm problems with solution in Python and hints

STRUCTURE: problem-type -> leetcodenumber-task-name -> task, hints (optional), solution
from: https://leetcode.com/studyplan/leetcode-75/

TODO:

1. fix 104 -> 10^4 in task 2. separate tests from solution 3. in test cases use named arguments 4. pipeline (optional) 5. make leetcode-75 a separate folder, yandex - separate (also change readme)