【codeforces 651B - Beautiful Paintings 】 greedy(贪心)

最新推荐文章于 2017-02-27 16:49:05 发布

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本文探讨了如何通过最优排列一组画作的美丽值来最大化游客的幸福度。利用两个优先队列的数据结构，实现画作美丽值的有效比较与重新排列，最终得到使游客幸福度最大的画作展示顺序。

B. Beautiful Paintings
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

There are n pictures delivered for the new exhibition. The i-th painting has beauty ai. We know that a visitor becomes happy every time he passes from a painting to a more beautiful one.

We are allowed to arranged pictures in any order. What is the maximum possible number of times the visitor may become happy while passing all pictures from first to last? In other words, we are allowed to rearrange elements of a in any order. What is the maximum possible number of indices i (1 ≤ i ≤ n - 1), such that ai + 1 > ai.
Input

The first line of the input contains integer n (1 ≤ n ≤ 1000) — the number of painting.

The second line contains the sequence a1, a2, …, an (1 ≤ ai ≤ 1000), where ai means the beauty of the i-th painting.
Output

Print one integer — the maximum possible number of neighbouring pairs, such that ai + 1 > ai, after the optimal rearrangement.
Examples
Input

5
20 30 10 50 40

Output

Input

4
200 100 100 200

Output

Note

In the first sample, the optimal order is: 10, 20, 30, 40, 50.

In the second sample, the optimal order is: 100, 200, 100, 200.

题意：：游客在欣赏画时，通常会因为当前这幅画比前一幅画美丽而获得一点幸福度。给出n副画作的美丽值，现在要将他们排成一行。求出游客能获得的最大幸福值。

思路：两个优先队列维护（互相倒）

代码：

#include<iostream>
#include<stdio.h>
#include<string.h>
#include<queue>
using namespace std;
int n;
int ans;
int a[10005];
priority_queue<int> q1,q2;
int main()
{
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
    {

        scanf("%d",&a[i]);
        q1.push(-a[i]);
    }
    int now;
    while((!q1.empty())||(!q2.empty()))
    {

        if(!q1.empty()) now=q1.top(),q1.pop();
        while(!q1.empty())
        {
            int nex=q1.top();
            q1.pop();
            if(nex<now)
            {
                ans++;
                now=nex;
            }
            else q2.push(nex);
        }
        if(!q2.empty()) now=q2.top(),q2.pop();
        while(!q2.empty())
        {
            int nex=q2.top();
            q2.pop();
            if(nex<now)
            {
                ans++;
                now=nex;
            }
            else q1.push(nex);
        }
    }
    printf("%d\n",ans);
}