In this task, you are given a list of unique integers you need to swap the positions of maximum and minimum element in the list and return the updated list.
Q: [331, 255, 149, 439, 494, 421, 356, 361, 394, 496, 342, 396, 137, 364, 189, 47, 174, 353, 220, 219]
A: 
[331, 255, 149, 439, 494, 421, 356, 361, 394, 47, 342, 396, 137, 364, 189, 496, 174, 353, 220, 219]