Day 15: Killing groups

Now that the engine can see groups and count liberties (and see where are the liberties), the obvious step is to see if a group is killed. Basically when someone plays the board will look using the ruleset if any group have 0 liberties. If it is the case, all those positions becomes empty (value of the position = 0), and the number of dead stones should increase to a "dead stones" variable for the outsider or the engine.

This is the "search for liberties" method (I didn't publish it yesterday, you have it now):

public ArrayList<integer> getLiberties(ArrayList<integer> group, Board board){ //given a group, I should count liberties. ArrayList<integer> liberties=new ArrayList<>(); int groupPointer=0; for(int i=0;i<group.size();i++){ //search to the right if(board.getMove(group.get(i)+1)==0){ if(liberties.contains(group.get(i)+1)==false){ liberties.add(group.get(i)+1); } } //search to the left if(board.getMove(group.get(i)-1)==0){ if(liberties.contains(group.get(i)-1)==false){ liberties.add(group.get(i)-1); } } //search up if(board.getMove(group.get(i)-(board.getBoardSize()+1))==0){ if(liberties.contains(group.get(i)-(board.getBoardSize()+1))==false){ liberties.add(group.get(i)-(board.getBoardSize()+1)); } } //search down if(board.getMove(group.get(i)+(board.getBoardSize()+1))==0){ if(liberties.contains(group.get(i)+(board.getBoardSize()+1))==false){ liberties.add(group.get(i)+(board.getBoardSize()+1)); } } } return liberties; }

I need a new method in the ruleset that analizes a group and if it have 0 liberties will return true. Else will return false.


public boolean TryKillingGroups(ArrayList<integer> group,Board board){ //this receives a group, if it does not have any //liberty it returns true the group have 0 liberties //and is dead. ArrayList<integer> liberties=this.getLiberties(group, board); //If liberties==0 then is dead, else is alive. if(liberties.isEmpty()==true){ return true; }else{ return false; } }

And, the board should be the responsible of killing the stones. So, in the board class, I create a method that given a color It should see if there is any group without liberties:


public void tryToKill(int color){ Ruleset ruleset=new Ruleset(); ArrayList<integer> group=new ArrayList<>(); boolean isDead; for(int i=0;i<this.getMainBoard().size();i++){ if(this.getMove(i)==color){ group=ruleset.getGroup(i, this); isDead=ruleset.TryKillingGroups(group, this); if(isDead==true){ //if dead KILL! System.out.println("Killed"); for(int j=0;j<group.size();j++){ this.setMove(group.get(j), 0); } } } } }
And the last step: in the main board, when someone plays something (that is not "pass" or "resign") it should first see if there is something dead for the opposite color that is played and kill it.