I think the following problem is a good exercise. In a List of Lists, merge lists which define neighbour intervals: for example,

list = {{1,2},{3.5,4.5},{4.5,10},{10,11},{13,14}}

should be "merged" as


It can be assumed that the elements are in the right order (i.e., not as in {{1,2},{3.5,4.5},{13,14},{4.5,10},{10,11}}. One way of doing it the following:

Select[Tally@Flatten@list, #[[2]] == 1 &][[All, 1]] // Partition[#, 2] &

It flattens list and keep the elements which appear only once, then partition. But I'm sure there are other possibly better solutions. Any ideas?

  • 6
    $\begingroup$ List@@Interval@@list $\endgroup$
    – LouisB
    Commented Nov 9, 2016 at 6:43

1 Answer 1



IntervalUnion @@ (Interval /@ list) /. x_[y__] :> {y}


{{1, 2}, {3.5, 11}, {13, 14}}

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