Codeforces 492B Vanya and Lanterns(水)

题目链接：Codeforces 492B Vanya and Lanterns

注意头尾不存在灯的情况

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
const int maxn = 1005;

int N, L, pos[maxn];

int main () {
	scanf("%d%d", &N, &L);
	for (int i = 0; i < N; i++)
		scanf("%d", &pos[i]);
	sort(pos, pos + N);
	double ans = max(pos[0] - 0, L - pos[N-1]);
	for (int i = 1; i < N; i++)
		ans = max(ans, (pos[i] - pos[i-1]) / 2.0);
	printf("%.10lf\n", ans);
	return 0;
}