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fixed typos in picasso

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Signed-off-by: Julien CLEMENT <julien.clement@epita.fr>
This commit is contained in:
Julien CLEMENT 2023-05-04 20:35:51 +02:00
parent 3d25b6e1ea
commit 3233d4a1a0
1 changed files with 11 additions and 7 deletions
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jujure/content/writeups/fcsc_2023/picasso.md
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@ -189,8 +189,10 @@ iterating to find at which index is the byte from the `state` inside the
select an `allowed_moves` sub-array based on where the `state` byte is located select an `allowed_moves` sub-array based on where the `state` byte is located
in the `board`. in the `board`.
Good, so once we find out `state` byte inside `board` we start iterating over Good, so once we find our `state` byte inside `board` we start iterating over
the `allowed_moves`, basically the move is multiplied by `0xf`, which will effectively set the 4 bits corresponding to the single bit in the initial move, this will now be used as a mask on the board. the `allowed_moves`, basically the move is multiplied by `0xf`, which will
effectively set the 4 bits corresponding to the single bit in the initial move,
this will now be used as a mask on the board.
So this move simply selects an hex digit from the board actually, if the So this move simply selects an hex digit from the board actually, if the
selected byte is NOT 0, then we continue the loop, skipping the move, but if it selected byte is NOT 0, then we continue the loop, skipping the move, but if it
@ -241,7 +243,7 @@ are allowed according to were the hex digit was in the board.
- If a valid move was found, then we swap the `0` and the `state` byte. - If a valid move was found, then we swap the `0` and the `state` byte.
FINALLY, there is the final check, after all the moves from the state have been applied, the board must be `0x123456789abcdf0`. FINALLY, there is the final check, after all the moves from the state have been applied, the board must be `0x123456789abcdef0`.
Great, now let's look at the `allowed_moves`. Great, now let's look at the `allowed_moves`.
@ -285,8 +287,8 @@ OK so I got this one super fast actually, let's just get you the context back:
- each can be applied `[0;4[` times each time - each can be applied `[0;4[` times each time
- `0x36 == 54` elements in the state - `0x36 == 54` elements in the state
If you are a puzzle fan you already what this is I don't even need to show you If you are a puzzle fan you already know what this is I don't even need to show
the permutation matrix again but hey: you the permutation matrix again but hey:
```c ```c
char permutations[0x6][0x36] = char permutations[0x6][0x36] =
@ -324,7 +326,7 @@ It's a rubiks cube.
Each permutation table is a counter-clockwise rotation of a face of the cube. Each permutation table is a counter-clockwise rotation of a face of the cube.
The process of mapping the cube in its flattened representation and to know The process of mapping the cube in its flattened representation and to know
which permutations corresponds to which face is just teadious so I will juste which permutations corresponds to which face is just teadious so I will just
give you this one out. give you this one out.
Do keep in mind that I was not familiar with standard rubiks cube notations, so Do keep in mind that I was not familiar with standard rubiks cube notations, so
@ -447,7 +449,9 @@ tile to go to that location if there were no other tile on the grid. For example
tile `f` placed in the top left corner will have a manhattan distance of 5 to tile `f` placed in the top left corner will have a manhattan distance of 5 to
its supposed location. its supposed location.
So whenever the move counter of a tile becomes lower than its manhattant distance to its suppose location, you know that you will never be able to place the tile back to where it is supposed to be. So whenever the move counter of a tile becomes lower than its manhattant
distance to its supposed location, you know that you will never be able to place
the tile back to where it is supposed to be.
### Solver ### Solver