Union of multiple ranges

Question

I have these ranges:

7,10
11,13
11,15
14,20
23,39

I need to perform a union of the overlapping ranges to give ranges that are not overlappi

Answer 1

Here is a one-liner using functools.reduce (assuming (x, 10) and (11, y) overlap):

reduce(
    lambda acc, el: acc[:-1:] + [(min(*acc[-1], *el), max(*acc[-1], *el))]
        if acc[-1][1] >= el[0] - 1
        else acc + [el],
    ranges[1::],
    ranges[0:1]
)

This begins with the first range and uses reduce to go through the rest of the ranges. It compares the last element (acc[-1]) with the next range (el). If they overlap, it replaces the last element with the min and max of the two ranges (acc[:-1:] + [min, max]). If they don't overlap, it simply puts this new range at the end of the list (acc + [el]).

Example:

from functools import reduce

example_ranges = [(7, 10), (11, 13), (11, 15), (14, 20), (23, 39)]

def combine_overlaps(ranges):
    return reduce(
        lambda acc, el: acc[:-1:] + [(min(*acc[-1], *el), max(*acc[-1], *el))]
            if acc[-1][1] >= el[0] - 1
            else acc + [el],
        ranges[1::],
        ranges[0:1],
    )

print(combine_overlaps(example_ranges))

Output:

[(7, 20), (23, 39)]