不太会用单调队列，求指点！

#include<cstdio>
#include<queue>
#include<algorithm>

using namespace std;

const int maxn = 1e5 + 5;

int n, s, t, num[maxn];
int minx = 10000, maxx = -10000;
void Input() {
	scanf("%d %d %d", &n, &s, &t);
	for (int i = 1; i <= n; ++i) {
		scanf("%d", &num[i]);
		minx = min(minx, num[i]);
		maxx = max(maxx, num[i]);
	}
}

bool Check(double u) {
	double sum[maxn];
	for (int i = 1; i <= n; ++i) {
		sum[i] = sum[i - 1] + num[i] - u;
	}
	deque<int> q;
	for (int i = 1; i <= n; ++i) {
		while (!q.empty() && sum[q.back()] > sum[i]) {
			q.pop_back();
		}
		q.push_back(i);
		while (!q.empty() && q.front() < i - t) {
			q.pop_front();
		}
		if (i >= s && sum[i] - sum[q.front()] > 0) {
			return true;
		}
	}
	return 0;
}

double ans;
void Binary_Search() {
	double l = minx, r = maxx;
	while (r - l > 0.0001) {
		double mid = (l + r) / 2;
		if (Check(mid) == true) {
			l = mid;
			ans = mid;
		} else {
			r = mid;
		}
	}
}

int main() {
	Input();
	Binary_Search();
	printf("%.3lf", ans);
	return 0;
}