题目描述

代码

#include <cstdio>
#define min(a, b) ((a) > (b) ? (b) : (a))
#define max(a, b) ((a) < (b) ? (b) : (a))

int n, m;
double arr[100005], sum[100005], brr[100005];
double min_v, ans, res;
inline int read() {
    int s = 0, f = 1;
    char ch = getchar();
    while (ch < '0' || ch > '9') {
        if (ch == '-') f = -1;
        ch = getchar();
    }
    while (ch >= '0' && ch <= '9') s = s * 10 + ch - '0', ch = getchar();
    return s * f;
}
void write(int x) {
    if (x > 9) write(x / 10); 
    putchar(x % 10 + '0');
}
int main() {
    n = read(), m = read();
    for (int i = 1; i <= n; ++i) arr[i] = read();
    double l = 0, r = 2000.0;
    ans = 0;
    while (r - l > 1e-4) {
        min_v = 2000.0, ans = 0.0;
        double mid = (l + r) / 2.0;
        for (int i = 1; i <= n; ++i) {
            brr[i] = arr[i] - mid;
            sum[i] = sum[i - 1] + brr[i];
        }
        for (int i = m; i <= n; ++i) {
            min_v = min(min_v, sum[i - m]);
            ans = max(ans, sum[i] - min_v);
        }
        if (ans > 0) res = mid, l = mid;
        else r = mid;
    }
    write((res + 0.0001) * 1000);
    return 0;
}