题解 | #路灯#

#include <stdio.h>
int main()
{
    int n,l;
    while(~scanf("%d %d\n",&n,&l))
    {
        int s[1001];
        for(int i=0;i<n;i++)
        {
            scanf("%d ",&s[i]);
        }
        for(int i=0;i<n-1;i++)
        {
            for(int j=i+1;j<n;j++)
            {
                if(s[i] > s[j])
                {
                    int t = s[i];
                    s[i] = s[j];
                    s[j] = t;
                }
            }
        }
        double max = s[0]-0;
        if(l-s[n-1] > max)
        {
            max = l-s[n-1];
        }
        for(int i=1;i<n-1;i++)
        {
            if((double)(s[i]-s[i-1])/2 > max)
            {
                max = (double)(s[i]-s[i-1])/2;
            }
            if((double)(s[i+1]-s[i])/2 > max)
            {
                max = (double)(s[i+1]-s[i])/2;
            }
        }
        printf("%.2lf\n",max);
    }
}