一个欧拉回路的应用实例。一个农夫要巡视农场，要求每条路都要来回走一遍（即每条路走两遍且两遍的方向不同），求其解决方案。该问题的核心问题就是如何求欧拉回路。-Application examples of a Euler. A farmer to farm inspections required every road should go back and forth again (that is the way to go twice and twice each in a different direction), seeking their solutions. The core issue of the problem is how to find an Euler tour.