
arXiv: 1810.11216
AbstractWe study online secretary problems with returns in combinatorial packing domains with n candidates that arrive sequentially over time in random order. The goal is to determine a feasible packing of candidates of maximum total value. In the first variant, each candidate arrives exactly twice. All 2n arrivals occur in random order. We propose a simple 0.5‐competitive algorithm. For the online bipartite matching problem, we obtain an algorithm with ratio at least 0.5721 − o(1), and an algorithm with ratio at least 0.5459 for all n ≥ 1. We extend all algorithms and ratios to k ≥ 2 arrivals per candidate. In the second variant, there is a pool of undecided candidates. In each round, a random candidate from the pool arrives. Upon arrival a candidate can be either decided (accept/reject) or postponed. We focus on minimizing the expected number of postponements when computing an optimal solution. An expected number of Θ(n log n) is always sufficient. For bipartite matching, we can show a tight bound of O(r log n), where r is the size of the optimum matching. For matroids, we can improve this further to a tight bound of O(r′ log(n/r′)), where r′ is the minimum rank of the matroid and the dual matroid.
ddc:004, FOS: Computer and information sciences, Combinatorial optimization, matching, packing problem, 005, 004, Matroids, online algorithm, secretary problem, Secretary Problem, Computer Science - Computer Science and Game Theory, Coupon Collector Problem, Computer Science - Data Structures and Algorithms, coupon collector problem, Online algorithms; streaming algorithms, Data Structures and Algorithms (cs.DS), matroids, Computer Science and Game Theory (cs.GT)
ddc:004, FOS: Computer and information sciences, Combinatorial optimization, matching, packing problem, 005, 004, Matroids, online algorithm, secretary problem, Secretary Problem, Computer Science - Computer Science and Game Theory, Coupon Collector Problem, Computer Science - Data Structures and Algorithms, coupon collector problem, Online algorithms; streaming algorithms, Data Structures and Algorithms (cs.DS), matroids, Computer Science and Game Theory (cs.GT)
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