The Complexity of Trie Index Construction

Douglas Comer, Ravi Sethi

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


True structures are a convenient way of indexing files in which a key consists of a number of attributes. Records correspond to leaves in the true. Retrieval proceeds by following a path from the root to a leaf, the choice of edges being determined by attribute values. The size of a trle for a file depends on the order in which attributes are tested. It is shown that determining minimal size tries is an NP-complete problem for several variants of tries and that, for tries m which leaf chains are deleted, determining the true for which average access time is minimal is also an NP-complete problem. These results hold even for files in which attribute values are chosen from a binary or ternary alphabet.

Original languageEnglish (US)
Pages (from-to)428-440
Number of pages13
JournalJournal of the ACM (JACM)
Issue number3
StatePublished - Jul 1 1977


  • average search time
  • complexity
  • reformation retrieval
  • trle indexes
  • true size

ASJC Scopus subject areas

  • Software
  • Control and Systems Engineering
  • Information Systems
  • Hardware and Architecture
  • Artificial Intelligence


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