Problem A
Cross
In the game of Sudoku, the objective is to place integers
between
In cross-hatching, we select one of the nine numbers and,
for each of its occurrences in the grid, cross out the
corresponding row, column and
The first image below shows a very sparsely filled in Sudoku
grid. However, even in this grid it is possible to deduce using
cross-hatching that the number in the top left cell is
![\includegraphics[width=0.7\textwidth ]{cross.png}](/problems/cross/file/statement/en/img-0001.png)
You will be given a partially filled-in grid. Your task is to repeatedly apply the cross-hatching method for different numbers until no more deductions can be made about any number.
The initial placement of the numbers in the grid may be
invalid. It is also possible that there will be no available
cell for a number in a
Input
Input will consist of
Output
If the input is valid and there is no contradiction while solving, you should output the grid in the same format it was given in, with cells filled in if their value can be deduced using cross-hatching. Otherwise, output “ERROR” (quotes for clarity).
Sample Input 1 | Sample Output 1 |
---|---|
..9...... .....4... .......4. ......... .4....... ......... ......... ......... ......... |
4.9...... .....4... .......4. ......... .4....... ......... ......... ......... ......... |
Sample Input 2 | Sample Output 2 |
---|---|
...1...6. 18...9... ..7.642.. 2.9..6.5. .43...72. .6.3..9.1 ..265.1.. ...2...97 .5...3... |
524137869 186529473 397864215 219476358 843915726 765382941 972658134 638241597 451793682 |
Sample Input 3 | Sample Output 3 |
---|---|
1........ ..1...... .......1. ......... ......... ......... ......... ......... ......... |
ERROR |
Sample Input 4 | Sample Output 4 |
---|---|
........2 ....1.... 1........ ......1.. ......... ......... ......... .......1. ......... |
ERROR |