Given a list of words, group together all the anagrams. Anagrams are words that contain the same letters rearranged.

Given a number 'n', generate all possible well-formed (balanced) parentheses strings of length 2*n. For instance, if n=3, you need to create all valid combinations like '((()))', '(()())', etc.

Determine if a given 9x9 Sudoku board is valid. Check if each row, column, and 3x3 subgrid contains the digits 1-9 without repetition.