CodeForces 492B Vanya and Lanterns（水题）

最新推荐文章于 2020-05-17 21:10:09 发布

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本文介绍了一种计算路灯照明半径的方法，通过输入路灯数量和街道长度，以及每个路灯的位置，来确定最小的照明半径，确保整条街道都能被照亮。

思路：水题

#include<bits\stdc++.h>
using namespace std;
#define LL long long
const int maxn = 1005;
int a[maxn];
int main()
{
     int n,l;
	 scanf("%d%d",&n,&l);
	 for(int i = 0;i<n;i++)
		 scanf("%d",&a[i]);
	 sort(a,a+n);
	 double ans = max(a[0],l-a[n-1]);
	 for(int i = 1;i<n;i++)
		 ans = max(ans,(a[i]-a[i-1])/2.0);
	 printf("%.10lf\n",ans);
}

Description

Vanya walks late at night along a straight street of length l, lit by n lanterns. Consider the coordinate system with the beginning of the street corresponding to the point 0, and its end corresponding to the point l. Then the i-th lantern is at the point a_i. The lantern lights all points of the street that are at the distance of at most d from it, where d is some positive number, common for all lanterns.

Vanya wonders: what is the minimum light radius d should the lanterns have to light the whole street?

Input

The first line contains two integers n, l (1 ≤ n ≤ 1000, 1 ≤ l ≤ 10⁹) — the number of lanterns and the length of the street respectively.

The next line contains n integers a_i (0 ≤ a_i ≤ l). Multiple lanterns can be located at the same point. The lanterns may be located at the ends of the street.

Output

Print the minimum light radius d, needed to light the whole street. The answer will be considered correct if its absolute or relative error doesn't exceed 10^- 9.

Sample Input

Input

7 15
15 5 3 7 9 14 0

Output

2.5000000000

Input

2 5
2 5

Output

2.0000000000

Hint

Consider the second sample. At d = 2 the first lantern will light the segment [0, 4] of the street, and the second lantern will light segment [3, 5]. Thus, the whole street will be lit.