class PeopleSorter
{

PeopleOrder myOrder;

 public PeopleSorter(PeopleOrder order)
 {
  myOrder=order;
 } 

 public void sort(Person [] a,int n)
 // Sort (in place) the first n people in array a. 
 // Uses selection sort, sorts by PeopleOrder object
 {
  int sorted,minPos;
  for(sorted=0;sorted<n;sorted++)
     {
      minPos=indexFirst(a,sorted,n);
      swap(a,sorted,minPos);
     }
 }

 private static void swap(Person [] a,int pos1,int pos2)
 // Swap the people at index pos1 and pos2 in array a
 {
  Person temp;
  temp=a[pos1];
  a[pos1]=a[pos2];
  a[pos2]=temp;
 }

 private int indexFirst(Person [] a,int pos1,int pos2)
 // Return the index of the first person in the portion
 // of array a starting at index pos1 and up to but not
 // including index pos2.
 {
  int i,pos=pos1;
  for(i=pos1+1; i<pos2; i++)
     if(myOrder.before(a[i],a[pos]))
        pos=i;
  return pos;
 }

}