平均值最大连续子区间

二分答案+前缀和+维护区间长度

题目要求：求区间长度>=F的平均值最大的连续子区间的平均值

#include<bits.stdc++.h>
using namespace std;
const int N = 100010;
int n, F;
double a[N], s[N];
bool check(double avg){
    for (int i = 1; i <= n; i ++ ) s[i] = s[i - 1] + a[i] - avg;
    double mins = 0;
    for (int k = F; k <= n; k ++ ){
        mins = min(mins, s[k - F]);
        if (s[k] >= mins) return true;
    }
    return false;
}
int main()
{
    scanf("%d%d", &n, &F);
    double l = 0, r = 0;
    for (int i = 1; i <= n; i ++ ){
        scanf("%lf", &a[i]);
        r = max(r, a[i]);
    }

    while (r - l > 1e-5){
        double mid = (l + r) / 2;
        if (check(mid)) l = mid;
        else r = mid;
    }

    printf("%d\n", (int)(r * 1000));

    return 0;
}