Toward a deterministic polynomial time algorithm with optimal additive query complexity

  • Authors:
  • Nader H. Bshouty;Hanna Mazzawi

  • Affiliations:
  • Technion-Israel Institute of Technology;Technion-Israel Institute of Technology

  • Venue:
  • MFCS'10 Proceedings of the 35th international conference on Mathematical foundations of computer science
  • Year:
  • 2010

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Abstract

In this paper, we study two combinatorial search problems: The coin weighing problem with a spring scale (also known as the vector reconstructing problem using additive queries) and the problem of reconstructing weighted graphs using additive queries. Suppose we are given n identical looking coins. Suppose that m out of the n coins are counterfeit and the rest are authentic. Assume that we are allowed to weigh subsets of coins with a spring scale. It is known that the optimal number of weighing for identifying the counterfeit coins and their weights is at least Ω (m log n/log m). We give a deterministic polynomial time adaptive algorithm for identifying the counterfeit coins and their weights using O (m log n/log m + m log log m) weighings, assuming that the weight of the counterfeit coins are greater than the weight of the authentic coin. This algorithm is optimal when m ≤ nc/log log n, where c is any constant. Also our weighing complexity is within log log m times the optimal complexity for all m. To obtain this result, our algorithm makes use of search matrices, the divide and conquer approach and the guess and check approach. When combining these methods with the technique introduced in [Optimally Reconstructing Weighted Graphs Using Queries. SODA, 2010], we get a similar positive result for the problem of reconstructing a hidden weighted graph using additive queries.