Fixable vertex
= Fixable vertex
A vertex is fixable when its district contains no proper directed descendant of that vertex. Equivalently, $\operatorname{dis}(v)\cap\operatorname{de}(v)=\{v\}$.
= Fixable vertex
A vertex is fixable when its district contains no proper directed descendant of that vertex. Equivalently, $\operatorname{dis}(v)\cap\operatorname{de}(v)=\{v\}$.