Algorithms for list structure condensation

  • Gary Lindstrom
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Abstract

The need to detect and merge redundant information is a familiar problem in data management. This paper presents a particular definition of redundancy in list structures, along with algorithms for its removal. The process, termedcondensation, transforms a list structure into a minimally sized equivalent structure in which each cell has a unique information content. The resulting structure is often smaller than the original, and permits substructure equivalence testing to be done by trivial address identity comparison. Three algorithms are presented, two for noncyclic structures and one for cyclic. The best time result in both cases isO(mn) for ann-cell structure withm cell equivalence classes. In the case of noncyclic structures, that speed is attained under bounded workspace if a free mark bit is assumed in each cell. The cyclic algorithm is illustrated by application to themode equivalence problem ofalgol 68.

Keywords

Operating System Equivalence Class Information Content Data Management Good Time 

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References

  1. 1.
    Donald E. Knuth,Fundamental Algorithms (Addison-Wesley, Reading, Massachusetts, 1968).Google Scholar
  2. 2.
    C. H. A. Koster, “On infinite modes,”Algol Bulletin, contribution AB 30.3.3 (February 1969).Google Scholar
  3. 3.
    Gary Lindstrom, “Scanning list structures without stacks or tag bits,”Inf. Proc. Letters 2(2):47–51 (1973).Google Scholar
  4. 4.
    Richard M. Karp, Raymond E. Miller, and Arnold L. Rosenberg, “Rapid identification of repeated patterns in strings, trees and arrays,” inProc. 4th Ann. Symp. on Th. of Comp. (May 1972), pp. 125–136.Google Scholar
  5. 5.
    Gary Lindstrom, “Copying list structures using bounded workspace,”Comm. ACM 17:198–202 (1974).Google Scholar
  6. 6.
    J. Kral, “The equivalence of modes and the equivalence of finite automata,”Algol Bulletin, contribution AB 35.4.5 (March 1973).Google Scholar

Copyright information

© Plenum Publishing Corporation 1974

Authors and Affiliations

  • Gary Lindstrom
    • 1
  1. 1.Department of Computer ScienceUniversity of PittsburghPittsburgh

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