输油管道问题

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#define MAX 100000

void ps(int a[],int low,int high)   //快速排序
{
       int key,i,j;

       i=low;

       j=high;

       key=a[low];

       if(low>high) return;

       while(i<j)

       {

              while(key<=a[j] && i<j )

                    j--;
a[i]=a[j];

              while(i<j && key>=a[i])

                     i++;

              if(low<high)

                     a[j]=a[i];

       }

       a[i]=key;

       ps(a,low,j-1);

       ps(a,i+1,high);

}


int main()

{

    int a[MAX],b[MAX];
int n,i,j,sum,mid;

    while(scanf("%d",&n)!=EOF)

       {

              for(i=0;i<n*2;i++)

              {

                     scanf("%d",&a[i]);

              }

              for(i=1,j=0;i<n*2;j++,i=i+2)

              {

                     b[j]=a[i];

              }

              ps(b,0,n-1);

             

              sum = 0;
  mid = b[(n-1) / 2];

              for(i = 0; i < n; i++)

                     sum += abs(b[i] - mid);   //找出中位数

              printf("%d\n",sum);

       }

    return 0;

}