图的最长路与最长圈

A survey on the longest paths and cycles in graphs

路和圈是图论最基本的概念之一，Euler图问题和Hamilton问题都可归结为路和圈的研究。此外，路和圈在特定图中存在条件是我们最为关注的问题，而最长路和最长圈的研究更是引人入胜。本文就此问题作了较全面的回顾，并提出一些问题，供研究、探讨。

Cycles and paths are basic concepts in graphs .Euler graph and Hamilton cycle are special cases. Furthermore ,the existence of cycles and paths in graphs is more interesting . Almost all research papers on this subject are surveyed. At the same time , open problems are posed for study.