How to generate Intervals from a given list?

Question

If I have a list

list={3,7,4,5,1}

how to get the List of Intervals /Ranges

result = {{1,3},{3,4},{4,5},{5,7}}

TomD · Accepted Answer · 2012-01-21 09:29:50Z

up vote 17 down vote accepted

Maybe

Partition[Sort@list, 2, 1]

giving

{{1, 3}, {3, 4}, {4, 5}, {5, 7}}

answered Jan 21 '12 at 9:29

TomD
2,2482516

Beat me to it - 7 secs! Deleting mine, and +1. – Leonid Shifrin Jan 21 '12 at 9:30

Brett Champion · Answer 2 · 2012-01-22 03:55:47Z

up vote 7 down vote

Tom's answer is canonical, but you could also use:

With[{s = Sort[list]}, Transpose[{Most[s], Rest[s]}]]

which seems to be marginally faster for large lists. (In which case most of the time is spent sorting.)

answered Jan 22 '12 at 3:55

Brett Champion
10.3k12775

2

Alternatively: Composition[Transpose, Through, {Most, Rest}, Sort][list]. – J. M.♦ Jan 22 '12 at 4:26

2 Answers