Eulerian Path
Concept
欧拉路径:如果图G中的一个路径包括每个边恰好一次,则该路径称为欧拉路径(Euler path)。
欧拉回路:如果一个回路是欧拉路径,则称为欧拉回路(Euler circuit)。
欧拉图:具有欧拉回路的图称为欧拉图。
半欧拉图:具有欧拉路径但不具有欧拉回路的图称为半欧拉图。
Properties
Euler Cycle
A necessary and sufficient condition:
Undirected Graph
if and only if every vertex has even degree
all of its vertices with nonzero degree belong to a single connected component
Directed Graph
if and only if every vertex has equal in degree and out degree
all of its vertices with nonzero degree belong to a single connected component
Euler Path
A necessary and sufficient condition:
Undirected Graph
if and only if exactly zero or two vertices have odd degree
all of its vertices with nonzero degree belong to a single connected component
Directed Graph
if and only if at most one vertex has
(out-degree) − (in-degree) = 1
, at most one vertex has(in-degree) − (out-degree) = 1
, every other vertex has equal in-degree and out-degree,all of its vertices with nonzero degree belong to a single connected component
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