R / SQL /Python : Extracting connected components from node-edge pairs

Question

I struggle to come up with a title that describes what I'm trying to solve, so please comment if you have a better title!

The solution can be in R, Python, or SQL (Aster TeraData SQL to be exact, though a solution any SQL language is very helpful for learning purposes)

The problem: Given a list of pairs of items in no particular order, generate an output that links together all pairs that are related with at least one link.

Here is a simple example using R:

colone = c("a","b","u","e","f","f","j","z")
coltwo = c("b","c","c","a","g","h","h","y")
d <- data.frame(colone, coltwo)
d
  colone coltwo
1      a      b
2      b      c
3      u      c
4      e      a
5      f      g
6      f      h
7      j      h
8      z      y

Desired output (in any easily-readable data structure):

(a,b,c,e,u)
(f,g,h,j)
(y,z)

Essentially, the input is representing a graph of nodes and edges. The desired out is a list of all objects within the graph that are connected.

Any help or thoughts would be appreciated!

Answer 1

In R, you could use the package igraph:

library(igraph)
gg <- graph.edgelist(as.matrix(d), directed=F)
split(V(gg)$name, clusters(gg)$membership)
#$`1`
#[1] "a" "b" "c" "u" "e"
#
#$`2`
#[1] "f" "g" "h" "j"
#
#$`3`
#[1] "z" "y"

And you can look at the graph using:

plot(gg)

This is based on an excellent answer by MrFlick here