# Draw a hash table

I try to draw a hash table. I find the following answer which draws a linked list. I modify the code a little bit, resulting in

\usetikzlibrary{decorations.pathreplacing,positioning, calc,shapes.multipart,chains,arrows}
\tikzset{listnode/.style={rectangle split, rectangle split parts=2,
draw, rectangle split horizontal}}
\tikzset{hashtable/.style={rectangle split, rectangle split parts=7,
draw, rectangle split}}

\begin{tikzpicture}[scale=.2, >=stealth, start chain]
\node[hashtable,on chain, inner sep=8pt] (H) {};
\node[listnode,on chain] (A) {$12$};
\node[listnode,on chain] (B) {$99$};
\node[listnode,on chain] (C) {$37$};
\node[on chain,inner sep=2pt] (D) {$\emptyset$};
\draw[*->] let \p1 = (H.center), \p2 = (H.two) in (\x1,\y2) -- (A);
\draw[*->] let \p1 = (A.two), \p2 = (A.center) in (\x1,\y2) -- (B);
\draw[*->] let \p1 = (B.two), \p2 = (B.center) in (\x1,\y2) -- (C);
\draw[*->] let \p1 = (C.two), \p2 = (C.center) in (\x1,\y2) -- (D);
\end{tikzpicture}


The code generates the following figure:

There are some points that I do not know how to fix:

1. The list nodes do not appear in the same line as the corresponding hash table slot.
2. I do not know how to adjust the arrow length.

This is the code for the original image (you can find it by looking at the revisions of this question). I don't use chain as I don't have much experience with it.

\documentclass[tikz]{standalone}
\usepackage{amssymb}
\usetikzlibrary{shapes.multipart,positioning,arrows,calc}
\tikzset{
listnode/.style={
rectangle split,rectangle split parts=2,draw,rectangle split horizontal,fill=blue!20
},
startnode/.style={
draw,minimum width=1.5cm,minimum height=.75cm
}
}
\begin{document}
\begin{tikzpicture}[scale=.2, >=stealth]
\node[startnode] (t0) {$T[0]$};
\node[startnode,below=0pt of t0] (t1) {$T[1]$};
\node[startnode,below=0pt of t1] (t2) {$T[2]$};
\node[listnode,right=of t0] (3) {3};
\node[listnode,right=of t1] (1) {1};
\node[listnode,right=.5cm of 1] (7) {7};
\node[listnode,right=of t2] (2) {2};
\node[listnode,right=.5cm of 2] (5) {5};
\node[listnode,right=.5cm of 5] (8) {8};
\node[right=.5cm of 3] (3x) {$\varnothing$};
\node[right=.5cm of 7] (7x) {$\varnothing$};
\node[right=.5cm of 8] (8x) {$\varnothing$};
\draw[*->] let \p1 = (3.two), \p2 = (3.center) in (\x1,\y2) -- (3x);
\draw[*->] let \p1 = (1.two), \p2 = (1.center) in (\x1,\y2) -- (7);
\draw[*->] let \p1 = (7.two), \p2 = (7.center) in (\x1,\y2) -- (7x);
\draw[*->] let \p1 = (2.two), \p2 = (2.center) in (\x1,\y2) -- (5);
\draw[*->] let \p1 = (5.two), \p2 = (5.center) in (\x1,\y2) -- (8);
\draw[*->] let \p1 = (8.two), \p2 = (8.center) in (\x1,\y2) -- (8x);
\draw[->] (t0) edge (3) (t1) edge (1) (t2) edge (2);
\end{tikzpicture}
\end{document}


As for the second diagram, finding the center anchor of H.two is a bit tricky.

\documentclass[tikz]{standalone}
\usepackage{amssymb}
\usetikzlibrary{decorations.pathreplacing,positioning, calc,shapes.multipart,chains,arrows}
\tikzset{listnode/.style={rectangle split, rectangle split parts=2,
draw, rectangle split horizontal}}
\tikzset{hashtable/.style={rectangle split, rectangle split parts=7,
draw, rectangle split}}
\begin{document}
\begin{tikzpicture}[scale=.2, >=stealth, start chain]
\node[hashtable,inner sep=8pt] (H) {};
\coordinate (x) at ($(H.text split)!.5!(H.two split)$);
\node[listnode,on chain] (A) at ($(x)+(10,0)$) {$12$};
\node[listnode,on chain] (B) {$99$};
\node[listnode,on chain] (C) {$37$};
\node[on chain,inner sep=2pt] (D) {$\varnothing$};
\draw[->] (x) -- (A);
\fill (x) circle (12.5pt); % I'm not sure what number to add here
\draw[*->] let \p1 = (A.two), \p2 = (A.center) in (\x1,\y2) -- (B);
\draw[*->] let \p1 = (B.two), \p2 = (B.center) in (\x1,\y2) -- (C);
\draw[*->] let \p1 = (C.two), \p2 = (C.center) in (\x1,\y2) -- (D);
\end{tikzpicture}
\end{document}


• Thanks. Is there a way to adjust the size of the "filled circle" in "*->". – Matteo Apr 10 at 12:45
• @Matteo You can do as my first arrow: use -> and then draw the circle manually. – user156344 Apr 10 at 14:41

the list nodes are relatively positioned from H.two east, used are orthogonal coordinates for positioning of the arrows' starts and nodes styles are slightly modified. from tikz libraries are present only used ones:

\documentclass[tikz, margin=3mm]{standalone}
\usetikzlibrary{arrows.meta,
chains,
positioning,
shapes.multipart}
\usepackage{amssymb}
\tikzset{hashtable/.style = {rectangle split,
rectangle split parts=7,
draw, inner sep=8pt},
listnode/.style = {rectangle split, rectangle split horizontal,
rectangle split parts=2,
draw, on chain},  % <---
every edge/.style = {draw, Circle-Stealth}    % <---
}
\begin{document}
\begin{tikzpicture}[
node distance = 0mm and 9mm,   % <---
start chain = A going right  % <---
]
%
\node[hashtable] (H) {};
\node[listnode, right=of H.two east] {$12$};    % <---, A-1
\node[listnode] {$99$};
\node[listnode] {$37$};
\node[on chain] {$\varnothing$};                % A-4
%
\draw   (H.two |- H.two east)       edge (A-1)  % <---
(A-1.two |- A-1.two east)   edge (A-2)
(A-2.two |- A-2.two east)   edge (A-3)
(A-3.two |- A-2.two east)   edge (A-4);
\end{tikzpicture}


gives

Use relative positioning to place nodes accordingly.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.pathreplacing,positioning, calc,shapes.multipart,chains,arrows}
\tikzset{listnode/.style={rectangle split, rectangle split parts=2,
draw, rectangle split horizontal}}
\tikzset{hashtable/.style={rectangle split, rectangle split parts=7,
draw, rectangle split}}

\begin{document}
\begin{tikzpicture}[scale=.2, >=stealth, start chain]
\node[hashtable,on chain, inner sep=8pt] (H) {};
\node[listnode,on chain,above right=-1.4cm and 0.7cm of H] (A) {$12$};
\node[listnode,on chain] (B) {$99$};
\node[listnode,on chain] (C) {$37$};
\node[on chain,inner sep=2pt] (D) {$\emptyset$};
\draw[*->] let \p1 = (H.center), \p2 = (H.two) in (\x1,\y2) -- (A.west);
\draw[*->] let \p1 = (A.two), \p2 = (A.center) in (\x1,\y2) -- (B.west);
\draw[*->] let \p1 = (B.two), \p2 = (B.center) in (\x1,\y2) -- (C.west);
\draw[*->] let \p1 = (C.two), \p2 = (C.center) in (\x1,\y2) -- (D);
\end{tikzpicture}
\end{document}


Regarding the arrow length, they depend on the node distance. If distance between two connecting nodes is more, the arrow length will be more.

• It is clearly preferable to make the starting point at the center. – user156344 Apr 10 at 9:32
• @JouleV I am trying that. But not sure now to do that. H.two is not located at the center – subham soni Apr 10 at 9:37
• It is the midpoint of segment joining H.text split and H.two split. Look at my answer and at page 796 of the TikZ - PGF manual. – user156344 Apr 10 at 9:49