Codeforces

Codeforces

题目描述：
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 ai. 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?
输入描述:
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 ai (0 ≤ ai ≤ l). Multiple lanterns can be located at the same point. The lanterns may be located at the ends of the street.
输出描述:
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.
输入：
7 15
15 5 3 7 9 14 0
2 5
2 5
输出：
2.5000000000
2.0000000000
题意：
入路灯数n和路长m，第二行输入路灯所在位置，然后计算路灯照射半径是多少才能覆盖整个路面。
题解：
直接从头到尾搞，注意两边就好了
代码：

#include<