直径为四的优美树

Graceful trees whose diameters are four

直径为四的树是否都是优美的 ,Huang等人认为这个问题是解决优美树猜想的一个关键问题 .本文根据树的结构 ,把直径为四的树分为两种类型 ,并将其优美性归结为文中定义的蒲公英的优美性 .同时证明了两类蒲公英的优美性 .

Whether all trees whose diameters are four are graceful? Huang and many other scholars believe that this question is the key to the Guess of Graceful trees.This paper divides all the trees whose diameters are four into two classes and reduce the graceful quality of them to the graceful quality of dandelion which is definited in this paper It also gives the proof of the graceful quality of two kinds of dandelion .