【题解】平均数

10 6
6
4
2
10
3
8
5
9
4
1

6500

#include<bits/stdc++.h>
using namespace std;
int n,m;
double a[100001],sum[100001],b[100001];
double eps=1e-5,l=-1e6,r=1e6;
double min(double x,double y){
    if(x>y)return y;else return x;
}
double max(double x,double y){
    if(x<y)return y;else return x;
}
int main(){
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    while(r-l>eps){
        double mid = (l+r)/2;
        double maxx=-1e10,minn=1e10;
        for(int i=1;i<=n;i++)b[i]=a[i]-mid;
        for(int i=1;i<=n;i++)sum[i]=sum[i-1]+b[i];
        for(int i=m;i<=n;i++){ 
            minn=(double)min(minn,sum[i-m]);
            maxx=(double)max(maxx,sum[i]-minn);
        }
        if(maxx>0)l=mid;else r=mid;
    }
    cout<<int(r*1000);
    return 0;
}