Who's in the Middle - poj 2388 (快速排序寻找中位数)

题意;

寻找中位数

利用快速排序来寻找中位数。

 #include <iostream>
 using namespace std;
 int N;
 int op[];
 int Median(int left,int right,int pos){
     int l=left-,r=left;
     int pirior=op[right];
     for(int i=left;i<right;i++){
         if(op[i]<pirior){
             int temp=op[i];
             op[i]=op[r];
             op[r]=temp;
             r++;
             l++;
         }
     }
     int t=op[right];
     op[right]=op[r];
     op[r]=t;
     if(r==pos){
         return op[r];
     }else if(r<pos){
         return Median(r+,right,pos);
     }if(r>pos){
         return Median(left,r-,pos);
     }

 }
 int main() {
     cin>>N;
     for(int i=;i<N;i++){
         cin>>op[i];
     }
     int mid=Median(,N-,N/);
     cout<<mid<<endl;
     return ;
 }

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 34962		Accepted: 20387

Description

FJ is surveying his herd to find the most average cow. He wants to know how much milk this 'median' cow gives: half of the cows give as much or more than the median; half give as much or less.

Given an odd number of cows N (1 <= N < 10,000) and their milk output (1..1,000,000), find the median amount of milk given such that at least half the cows give the same amount of milk or more and at least half give the same or less.

Input

* Line 1: A single integer N

* Lines 2..N+1: Each line contains a single integer that is the milk output of one cow.

Output

* Line 1: A single integer that is the median milk output.

Sample Input

5
2
4
1
3
5

Sample Output

3

Hint

INPUT DETAILS:

Five cows with milk outputs of 1..5

OUTPUT DETAILS:

1 and 2 are below 3; 4 and 5 are above 3.