摘要
The min-min problem of finding a disjoint path pair with the length of the shorter path minimized is known to be NP-complete (Xu et聽al., 2006) . In this paper, we prove that in planar digraphs the edge-disjoint min-min problem remains NP-complete and admits no -approximation for any unless . As a by-product, we show that this problem remains NP-complete even when all edge costs are equal (i.e., stronglyNP-complete). To our knowledge, this is the first NP-completeness proof for the edge-disjoint min-min problem in planar digraphs.