Two-terminal DAG

Two-terminal DAG --- двухполюсный бесконтурный орграф.

A two-terminal DAG (st-dag) [math]\displaystyle{ G }[/math] is a directed graph without any cycle, having a unique source [math]\displaystyle{ s }[/math] and a unique target [math]\displaystyle{ t }[/math]. This implies that an [math]\displaystyle{ st }[/math]-dag is weakly connected, namely, there is a path from [math]\displaystyle{ s }[/math] to any vertex and from any vertex to [math]\displaystyle{ t }[/math].