Finding a large hidden clique in a random graph

Noga Alon, Michael Krivelevich, Benny Sudakov

Research output: Contribution to journalArticlepeer-review

197 Scopus citations


We consider the following probabilistic model of a graph on n labeled vertices. First choose a random graph G(n, 1/2), and then choose randomly a subset Q of vertices of size k and force it to be a clique by joining every pair of vertices of Q by an edge. The problem is to give a polynomial time algorithm for finding this hidden clique almost surely for various values of k. This question was posed independently, in various variants, by Jerrum and by Kučera. In this paper we present an efficient algorithm for all k > cn0.5, for any fixed c > 0, thus improving the trivial case k > cn0.5(log n)0.5. The algorithm is based on the spectral properties of the graph.

Original languageEnglish (US)
Pages (from-to)457-466
Number of pages10
JournalRandom Structures and Algorithms
Issue number3-4
StatePublished - 1998
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Software
  • General Mathematics
  • Computer Graphics and Computer-Aided Design
  • Applied Mathematics


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