flatland-space-stations.rb

#!/bin/ruby
# https://www.hackerrank.com/contests/worldcodesprint/challenges/powerplants-in-flatland

n,m = gets.strip.split(' ')
n = n.to_i
m = m.to_i
c = gets.strip
c = c.split(' ').map(&:to_i)

max_distance = 0
closest_distance = 0
distance = 0

for i in (0...n)
    closest_distance = n
    c.each do |space_station|
        distance = (i - space_station).abs
        closest_distance = distance if distance < closest_distance
        break if closest_distance < max_distance
    end
    max_distance = closest_distance if closest_distance > max_distance
end
puts max_distance