Put a number in each cell without a number so that the number and arrow in each cell indicates how many different numbers exist in the direction the cell is pointing at (not including itself).
(Rule and example from PGP IB)
History of the puzzle
Invented by Masanori Natsuhara (Japan) in 1992. First appeared on July 1992 edition of the Puzzler magazine.
Original named "何種類?" ("how many kinds").
Japanese Arrows (Complete)
Enter a digit in every cell in the grid. The arrows indicate all of the 8 directions in which the number of different digits is equal to the number in the cell. All possible arrows are given.
(Rules and example from WPC 2018 IB)