/**
* Computes all of the states immediately reachable from this state and returns them as an array
* of states. You probably will not need to use this method directly, since ordinarily you will be
* expanding <tt>Node</tt>s, not <tt>State</tt>s.
*/
public State[] expand() {
int gridsize = puzzle.getGridSize();
int grid[][] = getGrid();
int num_cars = puzzle.getNumCars();
ArrayList<State> new_states = new ArrayList<State>();
for (int v = 0; v < num_cars; v++) {
int p = varPos[v];
int fp = puzzle.getFixedPosition(v);
boolean orient = puzzle.getCarOrient(v);
for (int np = p - 1; np >= 0 && (orient ? grid[fp][np] : grid[np][fp]) < 0; np--) {
int[] newVarPos = (int[]) varPos.clone();
newVarPos[v] = np;
new_states.add(new State(puzzle, newVarPos));
}
int carsize = puzzle.getCarSize(v);
for (int np = p + carsize;
(np < gridsize && (orient ? grid[fp][np] : grid[np][fp]) < 0)
|| (v == 0 && np == gridsize);
np++) {
int[] newVarPos = (int[]) varPos.clone();
newVarPos[v] = np - carsize + 1;
new_states.add(new State(puzzle, newVarPos));
}
}
puzzle.incrementSearchCount(new_states.size());
return (State[]) new_states.toArray(new State[0]);
}
/**
* Computes a grid representation of the state. In particular, an nxn two-dimensional integer
* array is computed and returned, where n is the size of the puzzle grid. The <tt>(i,j)</tt>
* element of this grid is equal to -1 if square <tt>(i,j)</tt> is unoccupied, and otherwise
* contains the index of the car occupying this square. Note that the grid is recomputed each time
* this method is called.
*/
public int[][] getGrid() {
int gridsize = puzzle.getGridSize();
int grid[][] = new int[gridsize][gridsize];
for (int i = 0; i < gridsize; i++) for (int j = 0; j < gridsize; j++) grid[i][j] = -1;
int num_cars = puzzle.getNumCars();
for (int v = 0; v < num_cars; v++) {
boolean orient = puzzle.getCarOrient(v);
int size = puzzle.getCarSize(v);
int fp = puzzle.getFixedPosition(v);
if (v == 0 && varPos[v] + size > gridsize) size--;
if (orient) {
for (int d = 0; d < size; d++) grid[fp][varPos[v] + d] = v;
} else {
for (int d = 0; d < size; d++) grid[varPos[v] + d][fp] = v;
}
}
return grid;
}