How to divide a set of overlapping ranges into non-overlapping ranges?

Question

Let\'s say you have a set of ranges:

• 0 - 100: \'a\'
• 0 - 75: \'b\'
• 95 - 150: \'c\'
• 120 - 130: \'d\'

Obviously, these range

Answer 1

I'd say create a list of the endpoints and sort it, also index the list of ranges by starting and ending points. Then iterate through the list of sorted endpoints, and for each one, check the ranges to see which ones are starting/stopping at that point.

This is probably better represented in code... if your ranges are represented by tuples:

ranges = [(0,100,'a'),(0,75,'b'),(95,150,'c'),(120,130,'d')]
endpoints = sorted(list(set([r[0] for r in ranges] + [r[1] for r in ranges])))
start = {}
end = {}
for e in endpoints:
    start[e] = set()
    end[e] = set()
for r in ranges:
    start[r[0]].add(r[2])
    end[r[1]].add(r[2])
current_ranges = set()
for e1, e2 in zip(endpoints[:-1], endpoints[1:]):
    current_ranges.difference_update(end[e1])
    current_ranges.update(start[e1])
    print '%d - %d: %s' % (e1, e2, ','.join(current_ranges))

Although looking at this in retrospect, I'd be surprised if there wasn't a more efficient (or at least cleaner-looking) way to do it.