LaTeX Forum

\documentclass{article}

\usepackage[all]{xy}
\begin{document}

\xygraph{
!{<0cm,0cm>;<1cm,0cm>:<0cm,1cm>::}
!{(0,0) }*+{\bullet}="1"
!{(1,0) }*+{\bullet}="3"
!{(2,0)}*+{\bullet}="5"
!{(3,0) }*+{\bullet}="7"
!{(4,0) }*+{\bullet}="9"
!{(5,0) }*+{\bullet}="11"
!{(6,0) }*+{\bullet}="13"
!{(7,0) }*+{\bullet}="15"
!{(0,-2) }*+{\bullet}="2"
!{(1,-2) }*+{\bullet}="4"
!{(2,-2) }*+{\bullet}="6"
!{(3,-2) }*+{\bullet}="8"
!{(4,-2) }*+{\bullet}="10"
!{(5,-2) }*+{\bullet}="12"
!{(6,-2) }*+{\bullet}="14"
!{(7,-2) }*+{\bullet}="16"
!{(3.5,2) }*+{\bullet_{s}}="s"
!{(3.5,-4) }*+{\bullet_{t}}="t"
"s":"1" "s":"3" "s":"5" "s":"7" "s":"9" "s":"11" "s":"13" "s":"15" 
"2":"t" "4":"t" "6":"t" "8":"t" "10":"t" "12":"t" "14":"t" "16":"t"
"1":"4" "3":"6" "5":"8" "11":"10" "13":"12" "15":"14"
"1":@{-->}"2" "3":@{-->}"4" "5":@{-->}"6" "7":@{-->}"8" "9":@{-->}"4"
"9":@{-->}"10" "11":@{-->}"12" "13":@{-->}"14" "15":@{-->}"16" 
  }
\end{document}

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{arrows}
\begin{document}
\begin{tikzpicture}[node distance=3cm,
  thick,main node/.style={circle,fill=blue!20,draw,font=\sffamily\Large\bfseries}]

  \node[main node] (1) {1};
  \node[main node] (2) [below left of=1] {2};
  \node[main node] (3) [below right of=2] {3};
  \node[main node] (4) [below right of=1] {4};

  \path (1) edge (4);
  \path (3) edge (4);
  \path (2) edge (3);
  \path (2) edge (4);
  \path (1) edge (2);
\end{tikzpicture}

\begin{tikzpicture}[node distance=2cm, thick,star/.style={circle,draw}]
  
  \node[star] (6) {6};
  \node[star] (4) [below right of=1] {4};
  \node[star] (3) [below of=4] {3};
  \node[star] (2) [right of=3] {2};
  \node[star] (5) [right of=4] {5};
  \node           (hlp) at (barycentric cs:5=0.5,2=0.5) {};
  \node[star] (1) [right of=hlp, node distance=1.6cm]  {1};
  \path (6) edge (4);
  \path (3) edge (4);
  \path (4) edge (5);
  \path (3) edge (2);
  \path (5) edge (2);
  \path (5) edge (1);
  \path (2) edge (1);
\end{tikzpicture}
\end{document}