确定组合重叠范围的多个日期范围的“基数”

Question

I'm looking for an algorithm to convert several date-ranges to their 'base' ranges.

This base level means, it has the lowest number of seperate date-ranges. So overlapping or back-to-back ranges should be merged to one range.

With two ranges the comparison is fairly simple:

if (endA >= startB && endB >= startA) > Overlap and merge them

But what if the mergedAB backs against a third daterange C...

A: 2 April - 10 April
B: 5 April - 14 April
C: 15 April - 25 April
D: 28 April - 1 May

Then this should result in:

2 April - 25 April
28 April - 1 May

Any pointers on how to tackle this algorithm? How do I determine the end of the itteration, eg when is the base reached??

Answer 1

If the original list can produce multiple ranges (which the sample data indicates), then it is important to process the original list in start date order.

The first element, A, becomes the baseRange, then subsequent elements are merged with the baseRange, not with the previous element. It is done with the range when the if returns false.