图布局算法探究（树，有向无环图，图等）

[leungwensen]

• https://cs.brown.edu/~rt/gdhandbook/
• http://cs.brown.edu/~rt/papers/gd-tutorial/gd-constraints.pdf
• http://graphics.stanford.edu/courses/cs448b-02-winter/lectures/treesgraphs/tree.graph.pdf
• http://www.cs.unc.edu/techreports/89-034.pdf
• https://en.wikipedia.org/wiki/Graph_drawing
• http://www.graphviz.org/Documentation/