Breadth and Depth-first search

Description

These functions return information on graph traversal by breadth and depth first search using routines from the BOOST library.

Usage

bfs(object, node, checkConn=TRUE)
dfs(object, node, checkConn=TRUE)

Arguments

Details

These two functions are interfaces to the BOOST graph library functions for breadth first and depth first search. Both methods handle unconnected graphs by applying the algorithms over the connected components.

Cormen et al note (p 542) that 'results of depth-first search may depend upon the order in which the vertices are examined ... These different visitation orders tend not to cause problems in practice, as any DFS result can usually be used effectively, with essentially equivalent results'.

Value

For bfs a vector of node indices in order of BFS visit.

For dfs a list of two vectors of nodes, with elements discover (order of DFS discovery), and finish (order of DFS completion).

Author(s)

VJ Carey <stvjc@channing.harvard.edu>

References

Boost Graph Library ( www.boost.org/libs/graph/doc/index.html )

The Boost Graph Library: User Guide and Reference Manual; by Jeremy G. Siek, Lie-Quan Lee, and Andrew Lumsdaine; (Addison-Wesley, Pearson Education Inc., 2002), xxiv+321pp. ISBN 0-201-72914-8

Examples

con1 <- file(system.file("XML/bfsex.gxl",package="RBGL"), open="r")
dd <- fromGXL(con1)
close(con1)

bfs(dd, "r")
bfs(dd, "s")

con2 <- file(system.file("XML/dfsex.gxl",package="RBGL"), open="r")
dd2 <- fromGXL(con2)
close(con2)

dfs(dd2, "u")

Results

R version 3.3.1 (2016-06-21) -- "Bug in Your Hair"
Copyright (C) 2016 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)

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> library(RBGL)
Loading required package: graph
Loading required package: BiocGenerics
Loading required package: parallel

Attaching package: 'BiocGenerics'

The following objects are masked from 'package:parallel':

    clusterApply, clusterApplyLB, clusterCall, clusterEvalQ,
    clusterExport, clusterMap, parApply, parCapply, parLapply,
    parLapplyLB, parRapply, parSapply, parSapplyLB

The following objects are masked from 'package:stats':

    IQR, mad, xtabs

The following objects are masked from 'package:base':

    Filter, Find, Map, Position, Reduce, anyDuplicated, append,
    as.data.frame, cbind, colnames, do.call, duplicated, eval, evalq,
    get, grep, grepl, intersect, is.unsorted, lapply, lengths, mapply,
    match, mget, order, paste, pmax, pmax.int, pmin, pmin.int, rank,
    rbind, rownames, sapply, setdiff, sort, table, tapply, union,
    unique, unsplit

> png(filename="/home/ddbj/snapshot/RGM3/R_BC/result/RBGL/bfs.Rd_%03d_medium.png", width=480, height=480)
> ### Name: bfs
> ### Title: Breadth and Depth-first search
> ### Aliases: bfs dfs dfs,graph,character,ANY-method
> ###   bfs,graph,character,logical-method dfs,graph,character,logical-method
> ###   bfs,graph,missing,logical-method bfs,graph,character,missing-method
> ###   dfs,graph,character,missing-method bfs,graph,missing,missing-method
> ###   dfs,graph,missing,missing-method bfs,graph-method
> ###   bfs,graph,character-method dfs,graph,character-method
> ###   bfs,graph,ANY,ANY-method
> ### Keywords: graphs
> 
> ### ** Examples
> 
> con1 <- file(system.file("XML/bfsex.gxl",package="RBGL"), open="r")
> dd <- fromGXL(con1)
> close(con1)
> 
> bfs(dd, "r")
[1] "r" "s" "v" "w" "t" "x" "u" "y"
> bfs(dd, "s")
[1] "s" "w" "r" "t" "x" "v" "u" "y"
> 
> con2 <- file(system.file("XML/dfsex.gxl",package="RBGL"), open="r")
> dd2 <- fromGXL(con2)
> close(con2)
> 
> dfs(dd2, "u")
$discovered
[1] "u" "v" "y" "x" "w" "z"

$finish
[1] "x" "y" "v" "u" "z" "w"

> 
> 
> 
> 
> 
> dev.off()
null device 
          1 
>