Leetcode ValidSudoku
Valid sudoku is an Array's exercise in Leetcode's Top Interview Questions. You are given a 2D array of characters that represents a Sudoku board. The array needs to be checked to ensure that no two digits are the same in each row, each column and each 3x3 box within the sudoku board.
This is quite a challenging exercise if you've not used for loops before. My solution has a bunch of nested for loops inside other loops.