原题链接:http://codeforces.com/problemset/problem/1003/C
Problem E
Time Limit : 8000/4000ms (Java/Other) Memory Limit : 524288/262144K (Java/Other)
Total Submission(s) : 2 Accepted Submission(s) : 0
Problem Description
Codeforces (c) Copyright 2010-2018 Mike Mirzayanov
Input
<p>The first line contains two integers $$$n$$$ and $$$k$$$ ($$$1 \le k \le n \le 5000$$$) the number of days in the given period, and the minimum number of days in a segment we consider when calculating <span class="tex-font-style-it">heat intensity value</span>, respectively.</p><p>The second line contains $$$n$$$ integers $$$a_1$$$, $$$a_2$$$, ..., $$$a_n$$$ ($$$1 \le a_i \le 5000$$$) the temperature measures during given $$$n$$$ days.</p>
Output
<p>Print one real number the <span class="tex-font-style-it">heat intensity value</span>, i. e., the maximum of <span class="tex-font-style-it">average temperatures</span> over all segments of not less than $$$k$$$ consecutive days.</p><p>Your answer will be considered correct if the following condition holds: $$$|res - res_0| < 10^{-6}$$$, where $$$res$$$ is your answer, and $$$res_0$$$ is the answer given by the jury's solution.</p>
Sample Input
4 3
3 4 1 2
Sample Output
2.666666666666667
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题目大意:
给出n个数,从中取m个数得平均值,m最小为k,求最大平均值。
思路:
前缀和+两层循环(第一层枚举m),开始的错因也在于没理解好 k是选数个数的最小值,仅仅认为m=k,so wrong。
最后注意控制一下精度就好了:
洛谷AC代码:
#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdio>
using namespace std;
int a[100100];
int sum[100100];
int main()
{
int n,k;
while(cin>>n>>k)
{
memset(a,0,sizeof(a));
memset(sum,0,sizeof(sum));
for(int i=1;i<=n;++i)
{
cin>>a[i];
sum[i]=sum[i-1]+a[i];
}
double ans=-9999999.0;
for(int j=k;j<=n;++j)
for(int i=j;i<=n;++i)
{
double t=(sum[i]-sum[i-j])*1.0/j;
if(t-ans>1e-8)ans=t;
}
printf("%.15lf\n",ans);
}
return 0;
}
The end;