Python: My short solution…

def flatlandSpaceStations(n, c):
    return max(
        (s := sorted(c))[0],  # dist.: 0 to 1st spaceport
        n - s[-1] - 1,  # dist.: last spaceport to n
        *map(lambda i: (s[i + 1] - s[i]) // 2,   # dist.: halfway between-
            range(len(s) - 1)))  # -each spaceport

I updated my code to make it more readable. Functional solutions aren't always difficult to read.