Looking to produce a tikz mindmap which gives the error missing number treated as zero l.9 . Can anyone tell me what the problem is?
\documentclass[10pt]{article}
\usepackage{tikz}
\usetikzlibrary{mindmap}
\begin{document}
\tikz [mindmap, every node/.style=concept, concept color=black!20, grow=cyclic,
level 1/.append style={level distance=4.5cm,sibling angle=90},
level 2/.append style={level distance=3.5cm, sibling angle=45}]
\node [root concept] {Computational Complexity} % root
child { node {Computational Problems}
child { node {Problem Measures} }
child { node {Problem Aspects} }
child { node {Problem Domains} }
child { node {Key Problems} }
}
child { node {Computational Models}
child { node {Turing Machines} }
child { node {Random-Access Machines} }
child { node {Circuits} }
child { node {Binary Decision Diagrams} }
child { node {Oracle Machines} }
child { node {Programming in Logic} }
}
child { node {Measuring Complexity}
child { node {Complexity Measures} }
child { node {Classifying Complexity} }
child { node {Comparing Complexity} }
child { node {Describing Complexity} }
}
child { node {Solving Problems}
child { node {Exact Algorithms} }
child { node {Randomization} }
child { node {Fixed-Parameter Algorithms} }
child { node {Parallel Computation} }
child { node {Partial Solutions} }
child { node {Approximation} }
};
\end{document}
