Nút, mũi tên và sơ đồ trong TikZ

\begin{tikzpicture}
  \node[draw] (a) at (0,0) {plain box};
  \node[draw, rounded corners, fill=blue!10] (b) at (3,0) {rounded};
  \node[draw, circle, fill=yellow!40] (c) at (5.5,0) {44};
  \node[draw, ellipse] (d) at (8,0) {ellipse};
  \node[draw, minimum width=2.5cm, minimum height=1cm] at (1,-1.6) {fixed size};
  \node[draw, text width=2.6cm, align=center] at (5,-1.6) {text that wraps onto two lines};
\end{tikzpicture}

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{positioning, arrows.meta}
\begin{document}
\begin{tikzpicture}[
    node distance=1.2cm and 1.6cm,
    box/.style={draw, rounded corners, fill=blue!8, minimum width=2.2cm, minimum height=0.8cm},
    >={Stealth},
  ]
  \node[box] (in) {Read data};
  \node[box, right=of in] (clean) {Clean};
  \node[box, right=of clean] (fit) {Fit model};
  \node[draw, circle, below=of clean] (ok) {OK?};
  \draw[->] (in) -- (clean);
  \draw[->] (clean) -- (fit);
  \draw[->] (fit) |- (ok);
  \draw[->] (ok) -| node[pos=0.75, left] {no} (in);
\end{tikzpicture}
\end{document}

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{positioning, arrows.meta}
\begin{document}
\begin{tikzpicture}[state/.style={draw, circle, minimum size=1cm}, >={Stealth}, node distance=2.4cm]
  \node[state, label=below:start] (s0) {$q_0$};
  \node[state, right=of s0] (s1) {$q_1$};
  \node[state, right=of s1, fill=green!15] (s2) {$q_2$};
  \draw[->] (s0) to[bend left] node[above] {$a$} (s1);
  \draw[->] (s1) to[bend left] node[below] {$b$} (s0);
  \draw[->] (s1) -- node[above] {$a$} (s2);
\end{tikzpicture}
\end{document}

\begin{tikzpicture}
  \node[draw, minimum width=3cm, minimum height=1cm] (box) {Server};
  \draw[->] (box.north) -- ++(0,0.7) node[above] {north};
  \draw[->] (box.east) -- ++(1,0) node[right] {east};
  \draw[->] (box.south west) -- ++(-0.6,-0.6) node[below left] {south west};
  \node[anchor=west] at (box.south east) {\small (anchor=west)};
\end{tikzpicture}

\begin{tikzpicture}
  \matrix[draw] {
    \node {a}; & \node {b}; \\
    \node {c}; & \node {d}; \\
  };
\end{tikzpicture}

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric}
\begin{document}
\begin{tikzpicture}
  \node[draw, diamond] at (0,0) {Yes?};
  \node[draw, ellipse] at (2.5,0) {ellipse works};
\end{tikzpicture}
\end{document}