Fill in different digits on each row and in each column. Next to the puzzle is stated which digits are valid. At some places there are < and > symbols between neighbouring squares. Then the digit to which the arrow is pointing, is the smallest of the two. As an example we will solve a puzzle with the digits 1 to 3.
The digit in the upperleft corner is smaller than the digit below it. This number itself is smaller than his right neighbour. Because only the digits 1, 2 and 3 are in the game, it must be that the 1 is in in the upperleft square, the 2 below it, and the 3 to the right of the 2.
Puzzles in this genre
On the second row and in the left column one digit is missing, but because we know everywhere there must be the digits 1, 2 and 3, it is clear what needs to be filled in.
The top row still needs two digits, the 2 and the 3. It is clear the middle square must be smaller than the 3 below it, so this must be the 2 and the 3 will be its righthand neighbour. Of the two missing digits that remain, we know which one is the largest, so we can complete the puzzle.