// what's the first step from now to get to bestSituation?
private String getNextStepToSituation(Situation situation_) {
System.out.println("retrieving first step to win...");
int lastStepRecorded = -1;
while (situation_._parentSituation != null) {
lastStepRecorded = situation_._actionLedToThisSituation;
situation_ = situation_._parentSituation;
System.out.println("going one step back...");
}
return AITools.columnToAction(lastStepRecorded);
}
public void computeNextSituations(int maxOrder_) {
if (_order >= maxOrder_) {
return;
}
int nextPlayer = _playerNumberMadeThisMove == 1 ? 2 : 1;
// check all possible actions
for (int col = 0; col < AITools.GRID_COLUMNS; col++) {
if (callback != null) {
callback.callback("beginning col " + col);
}
// next free row for this column
int nextFreeIndex = AITools.coordsToIndex(col, AITools.GRID_ROWS - 1);
while (_grid[nextFreeIndex] != 0) {
nextFreeIndex = AITools.getGridIndexOnTopOf(nextFreeIndex);
if (nextFreeIndex < 0) // can't throw in this row. no possible situation
{
break;
}
}
if (nextFreeIndex < 0) // can't throw in this row. no possible situation
{
continue;
}
// copy grid and apply new action
int[] newGrid = _grid.clone();
newGrid[nextFreeIndex] = nextPlayer;
if (_nextSituations == null) {
_nextSituations = new ArrayList<Situation>();
}
Situation newSituation = new Situation(col, nextPlayer, newGrid, _order + 1, this);
_nextSituations.add(newSituation);
newSituation._score = 0;
int gameStatus = AITools.getGameStatus(newGrid);
// compute follow Situations only if not a an end point
if (gameStatus == -1) {
newSituation.computeNextSituations(maxOrder_);
} else if (gameStatus == playerNumber) {
this._followingSituationsAreWins++;
// check: if this situation has the order 1 (next move) and is a win, then take it!
if (newSituation._order == 1) {
bestSituation = newSituation;
System.out.println("TAKE THE WIN: next move will finish match!");
AITools.visualizeGrid(newGrid);
break;
}
if (bestSituation._parentSituation == null
|| this._followingSituationsAreWins
> bestSituation._parentSituation._followingSituationsAreWins) {
// safety check: up to that situation, there may be no situation where the opponent has
// a winning chance!
if (!thereIsASafePathToWin(newSituation)) {
continue;
}
bestSituation = newSituation;
System.out.println(
"new best Situation with "
+ this._followingSituationsAreWins
+ " win chances with one piece.");
AITools.visualizeGrid(newGrid);
}
} else if (gameStatus != 0) // not draw game -> opponent wins
{
this._followingSituationsAreLosses++;
// System.out.println("found situation with score: " + newSituation._score);
// AITools.visualizeGrid(newGrid);
}
}
}