J4N J4N - 1 month ago 22
C# Question

Algorithm to detect overlapping periods

I've to detect if two time periods are overlapping.

Every period has a start date and an end date.

I need to detect if my first time period (A) is overlapping with another one(B/C).

In my case, if the start of B is equal to the end of A, they are not overlapping(the inverse too)

I found the following cases:

enter image description here

So actually I'm doing this like this:

tStartA < tStartB && tStartB < tEndA //For case 1
OR
tStartA < tEndB && tEndB <= tEndA //For case 2
OR
tStartB < tStartA && tEndB > tEndA //For case 3


(The case 4 is taken in account either in case 1 or in case 2)

It works, but it seems not very efficient.

So, first is there an existing class in c# that can modelize this(a time period), something like a timepsan, but with a fixed start date.

Secondly: Is there already a c# code(like in the Datetime class) which can handle this?

Third: if no, what would be your approach to make this comparison the most fast?

Answer

Simple check to see if two time periods overlap:

bool overlap = a.start < b.end && b.start < a.end;

or in your code:

bool overlap = tStartA < tEndB && tStartB < tEndA;

(Use <= instead of < if you change your mind about wanting to say that two periods that just touch each other overlap.)