说明：  普里姆(Prim)算法 （1）算法思想（2）较小紫边集的构造（3）候选紫边集合的修改(4）Prim算法的伪代码描述、、、、。
( Pu 閲屽 (Prim) the algorithm (1) the algorithm thought (2) the smaller purple on the one hand collection structure (3) candidate purple on the other hand gathers revision (4) Prim algorithm 浼唬鐮?description,. )