I have a vector of non-unique values that is quite long. 

I want to split this vector into four about equally long vectors, where no two vectors can contain the same value, but each of the four vectors may contain 1 or more different values.

Example: 

```
List <- c(1,1,1,2,3,3,5,5,5,5,9,11,11)

```

list1 = 1,1,1
list2 = 2,3,3
list3 = 5,5,5,5
list4 = 9,11,11

What is the best way to implement this in R?