JGAA Volumes Volume 23, no. 5, 2019 Special Issue on Selected Papers from the 12th International Conference and Workshops on Algorithms and Computation, WALCOM 2018 Guest Editor(s): M. Sohel Rahman, Wing-Kin Sung, and Ryuhei Uehara Guest Editors' Foreword M. Sohel Rahman, Wing-Kin Sung, and Ryuhei Uehara Vol. 23, no. 5, pp. 755-757, 2019. Approximating Partially Bounded Degree Deletion on Directed Graphs Vol. 23, no. 5, pp. 759-780, 2019. Regular paper. Faster algorithms for shortest path and network flow based on graph decomposition Manas Jyoti Kashyop, Tsunehiko Nagayama, and Kunihiko Sadakane Vol. 23, no. 5, pp. 781-813, 2019. Regular paper. Random Popular Matchings with Incomplete Preference Lists Suthee Ruangwises and Toshiya Itoh Vol. 23, no. 5, pp. 815-835, 2019. Regular paper. A Simple Algorithm for $r$-gatherings on the Line Vol. 23, no. 5, pp. 837-845, 2019. Regular paper.