MinMax Algorithm for Tic Tac Toe

I'm trying to do the MinMax for the tic tac toe (Always computer win) but I can't get it to work. All the successors simply return 0 (draw) as score and so the computer always chooses to move in the natural direction of the matrix.

PS: Matrix (class) is the board where they play, that contains an array of 9 positions.

| X | O | X | O | ... | like this.

Global Variable that handles the Tic Tac Toe board is called Main and is an instance of Matrix.

public void minMax(Matrix p) {
  Matrix bestvalue = maxValue(p);
  print(bestvalue);
  System.out.println(bestvalue.getScore());
  main = searchSucessorWithScore(p, bestvalue.getScore());
}

public Matrix maxValue(Matrix p) {
  if(endState(p)) { p.setScore(utility(p)); return p; } //always sets score to       0 but the method utility is correct...
  Matrix bestmove = new Matrix();
  bestmove.setScore(Integer.MIN_VALUE);
  LinkedList<Matrix> list = addSucessors(p, plays.PLAY_X);
  for(Matrix s : list) {
    Matrix move = minValue(s);
    if(move.getScore() > bestmove.getScore()) {
       bestmove = move;
    }
  }
  return bestmove;
}

public Matrix minValue(Matrix p) {
  if(endState(p)) { p.setScore(utility(p)); return p;}
  Matrix bestmove = new Matrix();
  bestmove.setScore(Integer.MAX_VALUE);
  LinkedList<Matrix> list = addSucessors(p, plays.PLAY_O);
  for(Matrix s : list) {
    Matrix move = maxValue(s);
    if(move.getScore() < bestmove.getScore()) { // <
      bestmove = move;
    }
  }
  return bestmove;
}

Auxiliar methods:

public LinkedList<Matrix> addSucessors(Matrix k, plays l) {
  LinkedList<Matrix> list = new LinkedList<Matrix>();
  for(int i=0; i<9; i++) {
  if(k.getRow(i).equals(plays.BLANK)) {
    Matrix p = k.clone();
    p.setRow(i, l);
    list.add(p);
  }
  }
return list;
}

/* RETURNS 0 FOR DRAW, 1 FOR PC WIN, -1 FOR USER WIN */
public int utility(Matrix p) {
  for(int i=0; i<9; i=i+3) {
    if(main.getRow(i).equals(plays.PLAY_X) && main.getRow(i+1).equals(plays.PLAY_X) && main.getRow(i+2).equals(plays.PLAY_X)) return 1;
    if(main.getRow(i).equals(plays.PLAY_O) && main.getRow(i+1).equals(plays.PLAY_O) && main.getRow(i+2).equals(plays.PLAY_O)) return -1;
  }
  for(int i=0; i<3; i++) {
    if(main.getRow(i).equals(plays.PLAY_X) && main.getRow(i+3).equals(plays.PLAY_X) && main.getRow(i+6).equals(plays.PLAY_X)) return 1;
    if(main.getRow(i).equals(plays.PLAY_O) && main.getRow(i+3).equals(plays.PLAY_O) && main.getRow(i+6).equals(plays.PLAY_O)) return -1;
  }
    if(main.getRow(0).equals(plays.PLAY_X) && main.getRow(4).equals(plays.PLAY_X) && main.getRow(8).equals(plays.PLAY_X)) return 1;
    if(main.getRow(2).equals(plays.PLAY_X) && main.getRow(4).equals(plays.PLAY_X) && main.getRow(6).equals(plays.PLAY_X)) return 1;
    if(main.getRow(0).equals(plays.PLAY_O) && main.getRow(4).equals(plays.PLAY_O) &&   main.getRow(8).equals(plays.PLAY_O)) return -1;
    if(main.getRow(2).equals(plays.PLAY_O) && main.getRow(4).equals(plays.PLAY_O) && main.getRow(6).equals(plays.PLAY_O)) return -1;
return 0;
}

public Matrix searchSucessorWithScore(Matrix p, Integer v) {
  for(Matrix s : addSucessors(p, plays.PLAY_X) {
  if(s.getScore() == v) return s;
  }
return null;
}

The method utility is correct, but inside recursion only returns 0 even for matrix's where there's a winner.

Help :D

---

There is not enough code posted to correctly assess, but this almost never works.

Integer v s.getScore() == v

You should be using Integer.intValue()

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