void OthelloBoard::UndoLastMove() {
   OthelloMove *m = (OthelloMove*)mHistory.back();
      // If last move was a pass, delete the pointer, pop off the stack and switch the player.
      if (m->IsPass()) {
      delete m;
      mHistory.pop_back();
      mNextPlayer = mNextPlayer * -1;
   }
    // Otherwise look through flipset class and switch back the pieces
   for (OthelloMove::FlipSet &s : m->mFlips) {
      int row = m->mRow + s.rowDelta, col = m->mCol + s.colDelta, enemy = s.switched;
      mBoard[m->mRow][m->mCol] = EMPTY; // set the last inputed piece as an empty spot
      while (enemy != 0) { // loop flipping the previous pieces
        mBoard[row][col] = mNextPlayer;
        enemy--;
      }
   }
    // Delete m pointer, switch player, and pop the history off the stack
   delete m;
   mNextPlayer = mNextPlayer * -1;
   mHistory.pop_back();

   // Get the new value of the board
    mValue = 0;
   for (int row = 0; row < BOARD_SIZE; row++) {
      for (int col = 0; col < BOARD_SIZE; col++) {
         mValue += mBoard[row][col];
      }
   }
}