Question

Let’s say I have the three following lists

A1
A2
A3

B1
B2

C1
C2
C3
C4
C5

I’d like to combine them into a single list, with the items from each list as evenly distributed as possible sorta like this:

C1
A1
C2
B1
C3
A2
C4
B2
A3
C5

I’m using .NET 3.5/C# but I’m looking more for how to approach it then specific code.

EDIT: I need to keep the order of elements from the original lists.

Answer 1

1. Take a copy of the list with the most members. This will be the destination list.

2. Then take the list with the next largest number of members.

3. divide the destination list length by the smaller length to give a fractional value of greater than one.

4. For each item in the second list, maintain a float counter. Add the value calculated in the previous step, and mathematically round it to the nearest integer (keep the original float counter intact). Insert it at this position in the destination list and increment the counter by 1 to account for it. Repeat for all list members in the second list.

5. Repeat steps 2-5 for all lists.

EDIT: This has the advantage of being O(n) as well, which is always nice 🙂