【英语时差8,16】怎样找出最短路径（下）

In the 1700′s the Swiss-born mathematician¹, Leonhard Euler worked out a way to tell whether or not a particular design was traceable in this way simply by counting the number of lines at each intersection² in the design. He found that if all the intersections³ had an even number of lines coming into them, then you could start at any point in the design and trace the whole thing without lifting your pen or going over any line twice. Today, a design that meets these requirements is called an Euler circuit after the eighteenth-century mathematician. So, if you’re planning a paper route, you might want to figure out whether the streets you’ve been given make up an Euler circuit. Once again, count the number of roads coming in to each intersection. If all intersections have an even number of roads, then you’re in luck.

1 mathematician   

n.数学家

参考例句：

• The man with his back to the camera is a mathematician.背对着照相机的人是位数学家。
• The mathematician analyzed his figures again.这位数学家再次分析研究了他的这些数字。

2 intersection   

n.交集，十字路口，交叉点；[计算机] 交集

参考例句：

• There is a stop sign at an intersection.在交叉路口处有停车标志。
• Bridges are used to avoid the intersection of a railway and a highway.桥用来避免铁路和公路直接交叉。

3 intersections   

n.横断( intersection的名词复数 )；交叉；交叉点；交集

参考例句：

• Traffic lights have been placed at all major intersections. 所有重要的交叉路口都安装了交通信号灯。
• Intersections are of the greatest importance in highway design. 在道路设计中，交叉口占有最重要的地位。 来自辞典例句