For an $m$-edge connected simple graph $G$, finding a spanning tree of $G$ with the maximum number of leaves is MAXSNP-complete. The problem remains NP-complete even if $G$ is planar and the maximal degree of $G$ is at most four. Lu and Ravi gave the first known polynomial-time approximation algorithms with approximation factors $5$ and $3$. Later, they obtained a $3$-approximation algorithm that runs in near-linear time. The best known result is Solis-Oba, Bonsma, and Lowski's $O(m)$-time $2$-approximation algorithm. We show an alternative simple $O(m)$-time $2$-approximation algorithm whose analysis is simpler. This paper is dedicated to the cherished memory of our dear friend, Professor Takao Nishizeki.

翻译：对于具有$m$条边的连通简单图$G$，寻找叶子数量最多的生成树问题是MAXSNP完全的。即使$G$是平面图且最大度数不超过4，该问题仍然是NP完全的。Lu和Ravi首次给出了近似因子为$5$和$3$的多项式时间近似算法。随后，他们提出了一种运行于近线性时间的3-近似算法。目前已知的最佳结果是Solis-Oba、Bonsma和Lowski的$O(m)$时间2-近似算法。我们提出了一种分析更简单的替代性$O(m)$时间2-近似算法。谨以此文纪念我们挚友西关贵夫教授。