Python: Dynamic interval data structure [closed]

问题

I am looking for some python code to efficiently compute interval overlaps. I've used the interval tree of the bx-python package before, but now need to delete intervals from the tree (or better yet, modify them). It seems the bx-python tree doesn't support this.

Any pointers?

回答1:

banyan supports deleting intervals from the tree. For example, to remove a minimal number of intervals from a list of intervals such that the intervals that are left do not overlap in O(n log n), banyan.SortedSet (augmented red-black tree) could be used:

from banyan import SortedSet, OverlappingIntervalsUpdator # pip install banyan

def maximize_nonoverlapping_count(intervals):
    # build "interval" tree sorted by the end-point O(n log n)
    tree = SortedSet(intervals, key=lambda (start, end): (end, (end - start)),
                     updator=OverlappingIntervalsUpdator)
    result = []
    while tree: # until there are intervals left to consider
        # pop the interval with the smallest end-point, keep it in the result
        result.append(tree.pop()) # O(log n)

        # remove intervals that overlap with the popped interval
        overlapping_intervals = tree.overlap(result[-1]) # O(m log n)
        tree -= overlapping_intervals # O(m log n)
    return result

Example:

print maximize_nonoverlapping_count([[3, 4], [5, 8], [0, 6], [1, 2]])
# -> [[1, 2], [3, 4], [5, 8]]

See Python - Removing overlapping lists.

回答2:

Maybe storing of all intersection intervals can help.

You need:

boundaries of union of all intervals,
for each intersection left boundary and list of intervals from which intersection is made.

Intersection intervals can be stored in a tree, because they are represented only with left boundary. Methods insert and delete interval look like (simplified):

Insert: find intersection intervals for left and right boundary of new interval, split these intersection intervals in 2 or 3 new intersection intervals. For each intersection intervals between add pointer to new interval.

Delete: find intersection intervals for left and right boundary, merge them to intersection intervals before. For each intersection intervals between remove pointer to deleted interval.

回答3:

If you're looking for a Python library that handles intervals arithmetic, consider python-interval. Disclaimer: I'm the maintainer of that library.

This library has support to check for overlaps, and to automatically merge intervals. For example:

>>> import intervals as I
>>> I.closed(1,2) | I.closed(2,3)
[1,3]
>>> I.closed(1,2).overlaps(I.closed(3,4))
False

If you want to specifically compute the overlap:

>>> I.closed(1,3) & I.closed(2, 4)
[2,3]

It supports open/closed intervals, finite or infinite. To remove intervals for a given one, just use the difference operator:

>>> I.closed(1, 4) - I.closed(2, 3)
[1,2) | (3,4]

I can help you if you can be a little bit more specific.

来源：https://stackoverflow.com/questions/4014242/python-dynamic-interval-data-structure

标签

python

overlap

intervals