Pure Sudoku

Sudoku is a placement puzzle, also known as Number Place in the United States. The aim of the puzzle is to enter a number from 1 through 9 in each cell of a grid,most frequently a 9×9 grid made up of 3×3 'regions', starting with various numbers given in some cells (the 'givens'). Each row, column and region must contain only one instance of each number. Completing the puzzle requires patience ...