Codeforces735B Urbanization 2016-12-13 11:58 114人阅读 评论(0) 收藏

B. Urbanization

time limit per test

2 seconds

memory limit per test

256 megabytes

input

standard input

output

standard output

Local authorities have heard a lot about combinatorial abilities of Ostap Bender so they decided to ask his help in the question of urbanization. There are n people
who plan to move to the cities. The wealth of the i of them is equal to ai.
Authorities plan to build two cities, first for n1 people
and second for n2 people.
Of course, each of n candidates can settle in only one of the cities. Thus, first some subset of candidates of size n1 settle
in the first city and then some subset of size n2 is
chosen among the remaining candidates and the move to the second city. All other candidates receive an official refuse and go back home.

To make the statistic of local region look better in the eyes of their bosses, local authorities decided to pick subsets of candidates in such a way that the sum of arithmetic mean of wealth of
people in each of the cities is as large as possible. Arithmetic mean of wealth in one city is the sum of wealth ai among
all its residents divided by the number of them (n1 or n2 depending
on the city). The division should be done in real numbers without any rounding.

Please, help authorities find the optimal way to pick residents for two cities.

Input

The first line of the input contains three integers n, n1 and n2 (1 ≤ n, n1, n2 ≤ 100 000, n1 + n2 ≤ n) —
the number of candidates who want to move to the cities, the planned number of residents of the first city and the planned number of residents of the second city.

The second line contains n integers a1, a2, ..., an (1 ≤ ai ≤ 100 000),
the i-th of them is equal to the wealth of the i-th
candidate.

Output

Print one real value — the maximum possible sum of arithmetic means of wealth of cities' residents. You answer will be considered correct if its absolute or relative error does not exceed 10 - 6.

Namely: let's assume that your answer is a, and the answer of the jury is b.
The checker program will consider your answer correct, if .

Examples

input

2 1 1
1 5

output

6.00000000

input

4 2 1
1 4 2 3

output

6.50000000

Note

In the first sample, one of the optimal solutions is to move candidate 1 to the first city and candidate 2 to
the second.

In the second sample, the optimal solution is to pick candidates 3 and 4 for
the first city, and candidate 2 for the second one. Thus we obtain (a3 + a4) / 2 + a2 = (3 + 2) / 2 + 4 = 6.5

——————————————————————————————————————————

题目的意思是在n个数里，取出n1和数和n2个数，不能重读，使得n1个数的算术平均数andn2个数的算术平均数和最大

我们用的的是贪心的思想，先把每个数从大到小排个序，然后取前n个数，这里贪心的把最大的几个数分到n1和n2种较

小的中，才能保证结果最大。

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;

bool cmp(long long a,long long b)
{
    return a>b;
}

int main()
{
int n,a,b;
double s[100005];
while(~scanf("%d%d%d",&n,&a,&b))
{
    for(int i=0;i<n;i++)
    scanf("%lf",&s[i]);
    sort(s,s+n,cmp);
   double  sum1=0;
    for(int i=0;i<min(a,b);i++)
    {
        sum1+=s[i];
    }
    double ave1=sum1/(min(a,b));

   double sum2=0;
    for(int i=min(a,b);i<a+b;i++)
    {
        sum2+=s[i];
    }
    double ave2=sum2/(max(a,b));

    printf("%.8f\n",ave1+ave2);
}
    return 0;
}