输油管道问题

#include <stdio.h>
#include <math.h>
int partition(int b[],int low,int high)
{
      int pivot,i,j;
      i=low;
      j=high;
      pivot=b[low];
      if(low>high) return;
      while(i<j)
      {
            while(pivot<=b[j] && i<j )
                  j--;
           if(i<j)
                  b[i]=b[j];
            while(pivot>=b[i] && i<j)
                  i++;
            if(low<high)
                  b[j]=b[i];
      }
      b[i]=pivot;
      partition(b,low,j-1);
      partition(b,i+1,high);
}
int main()
{
   int a[20004],b[10002],n,i,j,sum=0,mid;
   scanf("%d",&n);
   for(i=0;i<n*2;i++)
   {