You are given a list of integers nums representing coordinates of houses on a 1-dimensional line. You have 3 street lights that you can put anywhere on the coordinate line and a light at coordinate x lights up houses in [x - r, x + r], inclusive. Return the smallest r required such that we can place the 3 lights and all the houses are lit up.
n ≤ 100,000 where n is the length of nums
If we place the lamps on 3.5, 4.5 and 5.5 then with r = 0.5 we can light up all 4 houses.