RULES: Place a digit from 1 to 9 in each empty cell so that each digit appears exactly once in each row, column and 3x3 outlined box.
Horizontally adjacent cells marked by a diamond contain digits whose difference is equal to the first (leftmost) digit of the corresponding row.
Vertically adjacent cells marked by a diamond contain digits whose difference is equal to the first (topmost) digit of the corresponding column.
All such diamonds are marked.
