最优子结构 假设这是从到的最短通路，经过k If vertices i andare distinct,then we decompose path p into iwhere path pnow contains at most m-l edges.By Lemma 24.1. p'is a shortest path fromitok,ands)=(ik)ji k j 假设这是从i到j的最短通路，经过k p ’ 最优子结构