Relationships work ONLY when they are two-waystreets, with much give and take.
婚姻关系只有行驶在充分给予和获得的双向车道上才能成功。
2
A route is a sequence of one-waystreets connecting two intersections.
一条路径由一系列将两个路口连通的单行线组成。
3
Note that if not all of the streets are one-way, then we can obtain a digraph by drawing for each two-way road two directed edges, one in each direction.