N to N matching in scala

Question

I have two lists, namely

val a = List(1,2,3)

val b = List(4,5)

I want to perform N to N bipartite mapping and want to get output

List((1,4),(1,5),(2,4),(2,5),(3,4),(3,5))

How can I do this?

Is `B` a list or a pair? And why would you want the output to be a tuple instead of a list? — jub0bs, Sep 10 '15 at 08:44
B is a list. I am trying to find alternative for two nested "foreach" operation. — Mahek Shah, Sep 10 '15 at 08:51
FYI, what you're looking for is the *cartesian product* of two lists. — dcastro, Sep 10 '15 at 09:00
possible duplicate of [Cross product in Scala](http://stackoverflow.com/questions/14740199/cross-product-in-scala) — dcastro, Sep 10 '15 at 09:02

score 5 · Accepted Answer · answered Sep 10 '15 at 08:49

5

Assuming that B = List(4,5), then you can use for comprehensions to achieve your goal:

val A = List(1,2,3)
val B = List(4,5)

val result = for(a <- A; b <- B) yield {
  (a, b)
}

The output is

result:List[(Int, Int)] = List((1,4), (1,5), (2,4), (2,5), (3,4), (3,5))

answered Sep 10 '15 at 08:49

Till Rohrmann

score 1 · Answer 2 · answered Sep 10 '15 at 08:54

1

Consider also

a.flatMap(x => b.map(y => (x,y)))

though not so concise as a for comprehension.

answered Sep 10 '15 at 08:54

elm

2 Answers2