allMoves =  # list of moves made from the solved configuration
Solving a slide puzzle can be really tricky. We could program the computer to do it, but that would require us to figure out an algorithm that can solve the slide puzzle. That would be very difficult and involve a lot of cleverness and effort to put into this program.
Fortunately, there’s an easier way. We could just have the computer memorize all the random slides it made when it created the board data structure, and then the board can be solved just by performing the opposite slide. Since the board originally started in the solved state, undoing all the slides would return it to the solved state.
For example, below we perform a "right" slide on the board on the left side of the page, which leaves the board in the state that is on the right side of the page:
After the right slide, if we do the opposite slide (a left slide) then the board will be back in the original state. So to get back to the original state after several slides, we just have to do the opposite slides in reverse order. If we did a right slide, then another right slide, then a down slide, we would have to do an up slide, left slide, and left slide to undo those first three slides. This is much easier than writing a function that can solve these puzzles simply by looking at the current state of them.