POJ 3660 传递闭包 warshall算法
poj 1325 最小点覆盖

SPFA的两个优化(转)

scturtle posted @ 2010年8月26日 08:36 in algorithm , 3570 阅读

转自:http://aceeca1.frostbytez.com/index.php/archives/SPFA%E4%BC%98%E5%8C%96

  SLF:Small Label First 策略。
实现方法是,设队首元素为 $i$,队列中要加入节点 $j$,在 $d_j \le d_i$ 时加到队首而不是队尾,否则和普通的 SPFA 一样加到队尾。

  LLL:Large Label Last 策略。
实现方法是,设队列 $Q$ 中的队首元素为 $i$,距离标号的平均值为 $\overline d = \frac {\sum_{j \in Q} d_j }{\left| Q \right|}$,每次出队时,若 $d_i > \overline d$,把 $i$ 移到队列末尾,如此反复,直到找到一个 $i$ 使 $d_i \le \overline d$,将其出队。

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2022年9月29日 15:03

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