groovy/java check list intersections and combine elements

问题

I have a list:

def a = [[14, 17, 12, 5], [14, 17, 12, 8, 3], [5, 2], [9]]

I need to check intersections and if two lists intersect, combine them.

The result should be as follows:

def b = [[14, 17, 12, 5, 8, 3, 2], [9]]

(i.e 14 is in first sublist, which is also in second sublist, and recursively so on...) How this task can be solved?

回答1:

You can do something like this in Groovy:

def a = [[14, 17, 12, 5], [14, 17, 12, 8, 3], [5, 2], [9]]

def rslt = a.inject( [ ] ) { c, n ->
  for( cc in c ) {
    if( n.find { it in cc } != null ) {
      cc.addAll( n )
      cc = cc.unique()
      return c
    }
  }
  c << n
}

assert rslt == [[14, 17, 12, 5, 8, 3, 2], [9]]

回答2:

Here is another example using some of Groovy's set "inspired" methods on lists

def a = [[14, 17, 12, 5], [14, 17, 12, 8, 3], [5, 2], [9]]

def res = a.inject([]){ acc,val ->
    def isect =  acc.find{ val.intersect(it)}?.with{ it.addAll(val - it) }
    !isect ? acc << val : acc
}

assert res.containsAll([[14, 17, 12, 5, 8, 3, 2], [9]])

来源：https://stackoverflow.com/questions/15816396/groovy-java-check-list-intersections-and-combine-elements