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josch
91beb23e1f

9 years ago  

README.md  9 years ago  
cycles.py  9 years ago 
README.md
Finding all the elementary circuits of a directed graph
Algorithm by R. Tarjan
Enumeration of the elementary circuits of a directed graph
R. Tarjan, SIAM Journal on Computing, 2 (1973), pp. 211216
http://dx.doi.org/10.1137/0202017
Usage
echo "0 1\n0 2\n1 0\n1 3\n2 0\n3 0\n3 1\n3 2"  python cycles.py
First argument is the number of vertices. Ordered pairs of space separated vertices are given via standard input and make up the directed edges of the graph.
DOT file input
For simplicity, there is no DOT file parser included but the following allows to create a suitable argument string and standard input for simple DOT graphs.
Given a DOT file of a simple (no labels, colors, styles, only pairs of vertices...) directed graph, the following lines generate the number of vertices as well as the edge list expected on standard input.
sed n e '/^\s*[09]\+;$/p' graph.dot  wc l
sed n e 's/^\s*\([09]\) > \([09]\);$/\1 \2/p' graph.dot
The above lines work on DOT files like the following:
digraph G {
0;
1;
2;
0 > 1;
0 > 2;
1 > 0;
2 > 0;
2 > 1;
}
They would produce the following output:
3
0 1
0 2
1 0
2 0
2 1