C#

var distancesBetweenStations = new List<int>();
Array.Sort(c);
distancesBetweenStations.Add(c[0]);        
distancesBetweenStations.Add(n - c[c.Length - 1] - 1);
for (int i = 1; i < c.Length; i++)
{
    distancesBetweenStations.Add((c[i] - c[i-1])/2);
}
return (distancesBetweenStations.Max(j => j));