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【POJ3784】Running Median

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Running Median
Time Limit: 1000MS Memory Limit: 65536K
Total Submissions: 3406 Accepted: 1576

Description

For this problem, you will write a program that reads in a sequence of 32-bit signed integers. After each odd-indexed value is read, output the median (middle value) of the elements received so far.

Input

The first line of input contains a single integer P, (1 ≤ P ≤ 1000), which is the number of data sets that follow. The first line of each data set contains the data set number, followed by a space, followed by an odd decimal integer M, (1 ≤ M ≤ 9999), giving the total number of signed integers to be processed. The remaining line(s) in the dataset consists of the values, 10 per line, separated by a single space. The last line in the dataset may contain less than 10 values.

Output

For each data set the first line of output contains the data set number, a single space and the number of medians output (which should be one-half the number of input values plus one). The output medians will be on the following lines, 10 per line separated by a single space. The last line may have less than 10 elements, but at least 1 element. There should be no blank lines in the output.

Sample Input

3 
1 9 
1 2 3 4 5 6 7 8 9 
2 9 
9 8 7 6 5 4 3 2 1 
3 23 
23 41 13 22 -3 24 -31 -11 -8 -7 
3 5 103 211 -311 -45 -67 -73 -81 -99 
-33 24 56

Sample Output

1 5
1 2 3 4 5
2 5
9 8 7 6 5
3 12
23 23 22 22 13 3 5 5 3 -3 
-7 -3
解析:
動態維護中位數
方法:
建立兩個二叉堆:一個小根堆,一個大根堆。在依次讀入這個整數序列的過程中,設當前序列長度為M,我們始終保持:
1、序列中從小到大排名為1~M/2的整數存儲在大根堆中:
2、序列中從小到大排名為M/2+1~M的整數存儲在小根堆中。
任何時候,如果某一個堆中的元素過多,打破了這個性質,就取出該堆的堆頂插入另一個堆。這樣一來,序列的中位數就是小根堆的堆頂。
每次新讀入一個數值X後,若X比中位數小,則插入大根堆,否則插入小根堆,在插入之後檢查並維護上述性質即可。這就是“對頂堆”算法。
(本題對格式要求嚴格)
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
int T,n,m,a[50005];

priority_queue<int,vector<int>, greater<int> > q;//從小到大輸出:小頂堆 

priority_queue<int> p;//從大到小輸出 :大頂堆 

int main()
{
    scanf("%d",&T);
    while(T--)
    {
        while(!q.empty())q.pop();
        while(!p.empty())p.pop();
        scanf("%d%d",&m,&n);
        printf("%d %d\n",m,(n+1)/2);
        for(int i=1;i<=n;i++) scanf("%d",&a[i]);
        q.push(a[1]);
        printf("%d",a[1]);
        int cnt=1;
        for(int i=2;i<=n;i++)
        {
            if(a[i]>q.top()) q.push(a[i]);
            else p.push(a[i]);
            if(i%2!=0){
                while(p.size()>(i/2))
                {
                    q.push(p.top());
                    p.pop();
                }
                while(q.size()>(i-(i/2)))
                {
                    p.push(q.top());
                    q.pop();
                }
                cnt++;
                if(cnt%10==1) printf("\n%d",q.top());
                else printf(" %d",q.top());
            }    
        }
        puts("");//換行坑人...... 
    }
}            

【POJ3784】Running Median