Sudoku is a popular logic-based number placement puzzle. The goal is to fill a 9x9 grid with digits so that each column, each row, and each of the nine 3x3 subgrids that compose the grid (also called "boxes", "blocks", or "regions") contain all of the digits from 1 to 9. The puzzle starts with some cells already filled in, and the player must solve the remainder of the puzzle by filling in the empty cells. Here are the basic rules of Sudoku: 1. Each row must contain all digits from 1 to 9 with