What can be the efficient approach to solve the 8 puzzle problem?

Question

The 8-puzzle is a square board with 9 positions, filled by 8 numbered tiles and one gap. At any point, a tile adjacent to the gap can be moved into the gap, creating a new gap p

Answer 1

See this link for my parallel iterative deepening search for a solution to the 15-puzzle, which is the 4x4 big-brother of the 8-puzzle.