auto adjust node position in a binary tree

Question

I'm trying to draw a binary tree using tikz. I use shift option to define the relative position of child nodes. But as the tree grows, the nodes start to overlap if I use a fixed shift. I'm able to get around this by manually specifying the location of children nodes. But is there a better way to do it?

\documentclass{article} \usepackage{tikz} \usetikzlibrary{shapes.geometric,arrows,fit,matrix,positioning} \tikzset { treenode/.style = {circle, draw=black, align=center, minimum size=1cm}, subtree/.style = {isosceles triangle, draw=black, align=center, minimum height=0.5cm, minimum width=0.5cm, shape border rotate=90, anchor=north}, process/.style={rectangle, minimum width=2cm, minimum height=1cm, align=center, text width=2cm, draw}, connector/.style={circle, minimum size=1cm, align=center, text width=0.5cm, draw}, arrow/.style={thick, ->, >=stealth} } \usepackage{circuitikz} \begin{document} \begin{tikzpicture} \newcommand\xShift{1.5} \newcommand\yShift{1} \node(x) [treenode] at (0, 0) {100}; \node(xl) [treenode] at ([shift=({-\xShift,-\yShift})]x) {50}; \node(xr) [treenode] at ([shift=({\xShift,-\yShift})]x) {200}; \node(xll) [treenode] at ([shift=({-\xShift,-\yShift})]xl) {25}; \node(xlr) [treenode] at ([shift=({\xShift,-\yShift})]xl) {70}; \node(xlll) [ground] at ([shift=({-\xShift,-\yShift})]xll) {}; \node(xllr) [subtree] at ([shift=({\xShift,-\yShift})]xll) {}; \node(xlrl) [treenode] at ([shift=({-\xShift,-\yShift})]xlr) {60}; \node(xlrr) [subtree] at ([shift=({\xShift,-\yShift})]xlr) {}; \draw[->] (x) -- (xl); \draw[->] (x) -- (xr); \draw[->] (xl) -- (xll); \draw[->] (xl) -- (xlr); \draw[->] (xll) -- (xlll); \draw[->] (xll) -- (xllr.north); \draw[->] (xlr) -- (xlrl); \draw[->] (xlr) -- (xlrr.north); \end{tikzpicture} \end{document}

enter image description here

Related question Draw a binary tree using tikz

thank you. I tried using it. But since I have three different shapes, it doesn't come out clean. For example, to connect 25 and its right subtree which is a triangle, I'm not able to specify that the arrow should be on the north of the triangle. — arunmoezhi
– arunmoezhi, Commented Nov 3, 2014 at 22:08

cfr · Accepted Answer · 2014-11-03 23:56:31Z

You might try using a matrix of nodes:

\documentclass[tikz,border=5pt]{standalone} \usetikzlibrary{shapes.geometric,matrix} \tikzset { treenode/.style = {circle, draw=black, align=center, text centered, minimum size=1cm}, subtree/.style = {isosceles triangle, draw=black, align=center, minimum height=0.5cm, minimum width=0.5cm, shape border rotate=90}, phantom/.style = {draw=none, minimum size=0pt, inner sep=0pt, outer sep=0pt}, } \usepackage{circuitikz} \begin{document} \begin{tikzpicture} \matrix (mat) [matrix of nodes, nodes={treenode}] { &[5mm] &[5mm] &[5mm] 100 &[5mm] \\[5mm] & & 50 & & 200 \\[5mm] & 25 & & 70 & \\[5mm] |[phantom]| {} & & 60 & & |[subtree]| {} \\ & & |[subtree]| {} & &\\ }; \node [ground] at (mat-4-1) {}; \begin{scope}[draw, ->] \draw (mat-1-4) -- (mat-2-3); \draw (mat-1-4) -- (mat-2-5); \draw (mat-2-3) -- (mat-3-2); \draw (mat-3-2) -- (mat-4-3); \draw (mat-2-3) -- (mat-3-4); \draw (mat-3-4) -- (mat-4-3); \draw (mat-3-4) -- (mat-4-5.north); \draw (mat-3-2) -- (mat-4-1.north); \end{scope} \end{tikzpicture} \end{document}

nodes

EDIT

In response to the correction in the comment: in this case you could just adjust the matrix accordingly. However, I would probably draw a tree in this case instead. For example:

\documentclass[tikz,border=5pt]{standalone} \usetikzlibrary{shapes.geometric} \usepackage{forest} \usepackage{circuitikz} \begin{document} \tikzset{/forest, subtree/.style={isosceles triangle, draw=black, align=center, minimum height=0.5cm, minimum width=0.5cm, shape border rotate=90, child anchor=north, anchor=north, tier=terminus}, terminus/.style={draw=none, inner sep=0pt, outer sep=0pt, minimum height=0pt, minimum width=0pt, tier=terminus}, } \begin{forest} for tree={ edge path={ \noexpand\path [->, \forestoption{edge}] (!u.parent anchor) -- (.child anchor) \forestoption{edge label}; }, calign=fixed edge angles, calign angle=45, circle, draw=black, align=center, text centered, minimum size=10mm, } [100 [50 [25 [, terminus, name=ground here] [, subtree] ] [70 [60] [, subtree] ] ] [200 ] ] \node [ground] at (ground here) {}; \end{forest} \end{document}

tree

I apologize for being not clear. The right child of 25 is a subtree and the left child of 70 is a node with value 60. I do not want them to overlap. — arunmoezhi
– arunmoezhi, Commented Nov 3, 2014 at 23:11
@arunmoezhi Hmm... yes, that would have been easier. See my update. The revised question is more straightforward: I'd assumed that the problem was needing nodes with multiple parents. If you don't need that, a tree is the simplest solution, I think. — cfr
– cfr, Commented Nov 3, 2014 at 23:57

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auto adjust node position in a binary tree

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