CS 6510 HW 1

Create a Sudoku solver that works on arbitrary board sizes.

The input to your program (supplied on standard input) is two positive integers, m and n, which are given on a single line in decimal notation separated by a space character. Next in the input will be m times n lines, each of which supplies n times m space-separated board elements. A board element is either an integer between 1 and m times n, inclusive, or it is an underscore character, _.

The numbers m and n define the shape of the board as having small regions that are m cells wide and n cells tall. The overall board has n such regions across and m regions down. The remaining input lines define the board content, scanning left to right and then top to bottom, where _ indicates a position that has not been determined. Your solver's job is to replace every _ with a number, and then print the resulting board back out – in the same form as the input, but with no underscores.

For example, the input

 2 3
 1 2 _ 4 5 6
 3 4 _ 6 1 2
 5 6 _ 2 3 4
 2 3 4 5 _ 1
 4 5 6 1 _ 3
 6 1 2 3 _ 5

represents a board