acwing 102 -利用二分枚举区间平均值

#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
#define maxn 110000
#define INF 0x3f3f3f3f
using namespace std;
double list[maxn];
double s[maxn];
int f, n;
double l, r;
int check(double mid) {
	//获得前缀和
	for (int i = 1; i <= n; i++) {
		s[i] = list[i] - mid;
		s[i] += s[i - 1];
	}
	double mi = 1e8;
	double mx = -1e8;
	for (int i = f; i <= n; i++) {//1---n之间枚举
		mi = min(mi, s[i - f]);//get最小起点
		mx = max(mx, s[i] - mi);//get最大区间和
	}
	if (mx <= 0) {//mid不行，大了
		return 0;
	}
	else return 1;
	return 0;
}
int main() {

	scanf("%d %d", &n, &f);
	for (int i = 1; i <= n; i++) {
		scanf("%lf", &list[i]);
	}
	l = -1e6;
	r = 1e6;
	double mid;
	while(r-l>1e-5) {
		mid = (l + r) / 2;
		if (check(mid)) {//mid可以,答案还可以更大
			l = mid;
		}
		else {
			r = mid;
		}
	}
	printf("%d\n", (int)(r*1000));
	return 0;
}