In 2011, Harrigan and Healy published a polynomial-time algorithm for one-sided crossing minimization for trees. We point out a counterexample to that algorithm, and show that one-sided crossing minimization is NP-hard for trees.

翻译：Harrigan与Healy于2011年发表了针对树的一侧交叉最小化问题的多项式时间算法。本文指出该算法的一个反例，并证明一侧交叉最小化对于树而言是NP-困难的。