R/approximation.R

In rlemon: R Access to LEMON Graph Algorithms

##' Finds the largest complete subgraph (clique) in an undirected graph
##' via approximation algorithms for the maximal clique problem.
##'
##' For details on LEMON's implementation, including differences between the
##' algorithms, see \url{https://lemon.cs.elte.hu/pub/doc/1.3.1/a00194.html}.
##' @title Solver for Largest Complete Subgroup (All Nodes Connected)
##' @param arcSources Vector corresponding to the source nodes of a graph's
##'   edges
##' @param arcTargets Vector corresponding to the destination nodes of a graph's
##'   edges
##' @param numNodes The number of nodes in the graph
##' @param algorithm Choices of algorithm include "GrossoLocatelliPullanMc".
##'   GrossoLocatelliPullanMc is the default.
##' @return A named list containing two entries: 1) "size": the clique size, and
##'   2) "members": the members of the clique.
##' @export
MaxClique <- function(arcSources,
                      arcTargets,
                      numNodes,
                      algorithm = "GrossoLocatelliPullanMc") {

  check_graph_vertices(arcSources, arcTargets, numNodes)
  check_algorithm(algorithm)

  algfn <- switch(algorithm,
         "GrossoLocatelliPullanMc" = GrossoLocatelliPullanMcRunner,
         stop("Invalid algorithm.")
         )
  result <- algfn(arcSources, arcTargets, numNodes)
  names(result) <- c("size", "members")
  return(result)
}