第二個(gè)搜索函數(shù)為私有成員函數(shù)S a v e S e a r c h，由插入和刪除操作來調(diào)用。S a v e S e a r c h不僅
包含了S e a r c h的功能，而且可把每一級(jí)中遇到的最后一個(gè)節(jié)點(diǎn)存放在數(shù)組l a s t之中
Given a graph G = (V, E), where every edge e has a nonnegative weight w(e), and a source vertex s in V, find the shortest path from s to every other vertex
