implications.java

void buildGraph() {
	int n = grid.length;
	for (int i = 0; i < n; i++) {
	  for (int j = i + 1; j < n; j++) {
        if (grid[i][j] == -1 || grid[j][i] == -1) continue;
        if (grid[i][j] == grid[j][i]) {
          if (grid[i][j] == 0) {
            imply(2 * i, not(2 * j));
            imply(2 * j, not(2 * i));
          } else {
            imply(not(2 * i), 2 * j);
            imply(not(2 * j), 2 * i);
          }
        } else if (grid[i][j] == 0) {
          imply(2 * i, 2 * j);
        } else {
          imply(2 * j, 2 * i);
        }
      }
	 }
}

void imply(int from, int to) {
  graph.get(from).add(to);
  reverse.get(to).add(from);
}

int not(int value) {
  return value ^ 1;
}