/* quickSort.cc    for use with sortMain.cc */
            // code by david saunders (taken from Sedgewick, page 118).  2/96
typedef int itemType;  
// Must be a type on which the comparator > can be used.

// these three defs are wanted by sortMain.cc
#define quickSort sort
char* id = "quick";
char* ate = "g(N) := N*log[2](N);";

// quickSort() uses partition() which uses swap().

inline void swap(itemType a[], int i, int j){
  itemType v = a[i]; a[i] = a[j]; a[j] = v;
  }

inline int partition(itemType a[], int lo, int hi){
  /* 
  Let v = a[hi]. partition() permutes the elements in the array so 
  that all elements less than v are at the beginning of a and 
  all the elements larger than v are at the end.  The resulting 
  index of v itself (between these two groups) is returned.
  */
  itemType v = a[hi]; 
  int i = lo - 1; 
  int j = hi; 
  for (;;) {
    while (v > a[++i]); // a[lo..i-1] are < v.
    while (a[--j] > v); // a[j+1..hi] are > v.
    if (i >= j) break; // partition almost done
    swap(a, i, j);
    }
  swap(a, i, hi);
  return i;
  }

void
quickSort(itemType a[], int lo, int hi){
  // The items of a[lo..hi] are permuted into sorted order.
  // Side effect: a[0] is overwritten.
  if (lo < hi) {
    int mid = partition(a, lo, hi);
    quickSort(a, lo, mid - 1);
    quickSort(a, mid + 1, hi);
    }
  // else one or no elements -- and that's already sorted.
  }