Moves.md

Possible moves and related checks

Code structure

A main function with a switch case, and a dedicated function for each case. Functions return 1 if move is valid and was applied, or 0 otherwise.

Calculating deltas

Getting a move, for example C3:C4, we convert it to the table coordinates, ((2, 2), (2, 3)) and we calculate the variation in line and col as dx and dy (always positive).

Functions to read and write in the table

We add an extra layer to handle reading and writing outside of the table:

• read outside returns empty
• write outside is ignored

So that we can keep the same logic.

Cases

dx = 0 and dy = 1 or dx = 1 and dy = 0

The move is valid if:

• the source color is mine
• the target color is empty

Then to apply the move:

• set the target color to source color
• set the source color to empty

dx = 0 and dy = 2 or dx = 2 and dy = 0

The move is valid if:

• the source and the next color are mine

Empty target?

Then to apply the move:

• set the target color to source color
• set the source color to empty

Enemy target?

The move is valid if:

• the target next color is empty

Then to apply the move:

• set the target color to source color
• set the target next color to enemy color
• set the source color to empty

dx = 0 and dy = 3 or dx = 3 and dy = 0

The move is valid if:

• the source and the next color are mine

Empty target?

Then to apply the move:

• set the target color to source color
• set the source color to empty

Enemy target? (one)

The move is valid if:

• the target next color is empty

Then to apply the move:

• set the target color to source color
• set the target next color to enemy color
• set the source color to empty

Enemy target? (two)

The move is valid if:

• the target double next color is empty

Then to apply the move:

• set the target color to source color
• set the target next color to source color
• set the target double next color to enemy color
• set the source color to empty
• set the source next color to empty

dx = 1 and dy = 1

The move is valid if:

• the source color is mine
• the target color is empty
• the two remaining colors are one mine and one empty

Then to apply the move:

• invert mine and empty on all the area

dx = 2 and dy = 1 or dx = 1 and dy = 2

The move is valid if:

• the source color is mine
• the target color is empty
• the four remaining colors are two mine and two empty, correctly placed

Then to apply the move:

• invert mine and empty on all the area