/// <summary>
/// Rearranges the array in ascending order, using the natural order.</summary>
/// <param name="a">a the array to be sorted</param>
///
public static void Sort(IComparable[] a)
{
int N = a.Length;
// 3x+1 increment sequence: 1, 4, 13, 40, 121, 364, 1093, ...
int h = 1;
while (h < N / 3)
{
h = 3 * h + 1;
}
while (h >= 1)
{
// h-sort the array
for (int i = h; i < N; i++)
{
for (int j = i; j >= h && OrderHelper.Less(a[j], a[j - h]); j -= h)
{
OrderHelper.Exch(a, j, j - h);
}
}
Debug.Assert(IsHsorted(a, h));
h /= 3;
}
Debug.Assert(OrderHelper.IsSorted(a));
}
// quicksort the subarray a[lo .. hi] using 3-way partitioning
private static void Sort(IComparable[] a, int lo, int hi)
{
if (hi <= lo)
{
return;
}
int lt = lo, gt = hi;
IComparable v = a[lo];
int i = lo;
while (i <= gt)
{
int cmp = a[i].CompareTo(v);
if (cmp < 0)
{
OrderHelper.Exch(a, lt++, i++);
}
else if (cmp > 0)
{
OrderHelper.Exch(a, i, gt--);
}
else
{
i++;
}
}
// a[lo..lt-1] < v = a[lt..gt] < a[gt+1..hi].
Sort(a, lo, lt - 1);
Sort(a, gt + 1, hi);
Debug.Assert(OrderHelper.IsSorted(a, lo, hi));
}
/// <summary>
/// Rearranges the array in ascending order, using the natural order.</summary>
/// <param name="a">the array to be sorted</param>
///
public static void Sort(IComparable[] a)
{
int N = a.Length;
// put smallest element in position to serve as sentinel
int exchanges = 0;
for (int i = N - 1; i > 0; i--)
{
if (OrderHelper.Less(a[i], a[i - 1]))
{
OrderHelper.Exch(a, i, i - 1);
exchanges++;
}
}
if (exchanges == 0) return;
// insertion sort with half-exchanges
for (int i = 2; i < N; i++)
{
IComparable v = a[i];
int j = i;
while (OrderHelper.Less(v, a[j - 1]))
{
a[j] = a[j - 1];
j--;
}
a[j] = v;
}
Debug.Assert(OrderHelper.IsSorted(a));
}
/***************************************************************************
* Helper functions to restore the heap invariant.
***************************************************************************/
private void swim(int k)
{
while (k > 1 && OrderHelper.Greater <Key>(pq[k / 2], pq[k]))
{
OrderHelper.Exch(pq, k, k / 2);
k = k / 2;
}
}
/// <summary>
/// Rearranges the subarray a[lo..hi] in ascending order, using the natural order.</summary>
/// <param name="a">a the array to be sorted</param>
/// <param name="lo">lo left endpoint</param>
/// <param name="hi">hi right endpoint</param>
///
public static void Sort(IComparable[] a, int lo, int hi)
{
for (int i = lo; i <= hi; i++)
{
for (int j = i; j > lo && OrderHelper.Less(a[j], a[j - 1]); j--)
{
OrderHelper.Exch(a, j, j - 1);
}
}
Debug.Assert(OrderHelper.IsSorted(a, lo, hi));
}
/// <summary>
/// Rearranges the subarray a[lo..hi] in ascending order, using a generic comparator.</summary>
/// <param name="a">a the array</param>
/// <param name="lo">lo left endpoint</param>
/// <param name="hi">hi right endpoint</param>
/// <param name="comparator">comparator the comparator specifying the order</param>
///
public static void Sort <T>(T[] a, int lo, int hi, Comparer <T> comparator)
{
for (int i = lo; i <= hi; i++)
{
for (int j = i; j > lo && OrderHelper.Less(a[j], a[j - 1], comparator); j--)
{
OrderHelper.Exch <T>(a, j, j - 1);
}
}
Debug.Assert(OrderHelper.IsSorted(a, lo, hi, comparator));
}
/// <summary>
/// Rearranges the array in ascending order, using the natural order.</summary>
/// <param name="a">a the array to be sorted</param>
///
public static void Sort(IComparable[] a)
{
int N = a.Length;
for (int i = 0; i < N; i++)
{
for (int j = i; j > 0 && OrderHelper.Less(a[j], a[j - 1]); j--)
{
OrderHelper.Exch(a, j, j - 1);
}
Debug.Assert(OrderHelper.IsSorted(a, 0, i));
}
Debug.Assert(OrderHelper.IsSorted(a));
}
/// <summary>
/// Rearranges the array in ascending order, using a comparator.</summary>
/// <param name="a">a the array</param>
/// <param name="comparator">comparator the comparator specifying the order</param>
///
public static void Sort(object[] a, System.Collections.Comparer comparator)
{
int N = a.Length;
for (int i = 0; i < N; i++)
{
for (int j = i; j > 0 && OrderHelper.Less(a[j], a[j - 1], comparator); j--)
{
OrderHelper.Exch(a, j, j - 1);
}
Debug.Assert(OrderHelper.IsSorted(a, 0, i, comparator));
}
Debug.Assert(OrderHelper.IsSorted(a, comparator));
}
private void sink(int k)
{
while (2 * k <= N)
{
int j = 2 * k;
if (j < N && OrderHelper.Greater <Key>(pq[j], pq[j + 1]))
{
j++;
}
if (!OrderHelper.Greater <Key>(pq[k], pq[j]))
{
break;
}
OrderHelper.Exch(pq, k, j);
k = j;
}
}
/// <summary>
/// Removes and returns a smallest key on this priority queue.</summary>
/// <returns>a smallest key on this priority queue</returns>
/// <exception cref="InvalidOperationException">if this priority queue is empty</exception>
///
public Key DelMin()
{
if (IsEmpty)
{
throw new InvalidOperationException("Priority queue underflow");
}
OrderHelper.Exch(pq, 1, N);
Key min = pq[N--];
sink(1);
pq[N + 1] = default(Key); // avoid loitering and help with garbage collection
if ((N > 0) && (N == (pq.Length - 1) / 4))
{
resize(pq.Length / 2);
}
Debug.Assert(isMinHeap());
return(min);
}
/// <summary>
/// Rearranges the array in ascending order, using a comparator.</summary>
/// <param name="a">a the array</param>
/// <param name="c">c the comparator specifying the order</param>
///
public static void Sort <T>(T[] a, Comparer <T> c)
{
int N = a.Length;
for (int i = 0; i < N; i++)
{
int min = i;
for (int j = i + 1; j < N; j++)
{
if (OrderHelper.Less <T>(a[j], a[min], c))
{
min = j;
}
}
OrderHelper.Exch(a, i, min);
Debug.Assert(OrderHelper.IsSorted(a, 0, i, c));
}
Debug.Assert(OrderHelper.IsSorted(a, c));
}
/// <summary>
/// Rearranges the array in ascending order, using the natural order.</summary>
/// <param name="a">a the array to be sorted</param>
///
public static void Sort(IComparable[] a)
{
int N = a.Length;
for (int i = 0; i < N; i++)
{
int min = i;
for (int j = i + 1; j < N; j++)
{
if (OrderHelper.Less(a[j], a[min]))
{
min = j;
}
}
OrderHelper.Exch(a, i, min);
Debug.Assert(OrderHelper.IsSorted(a, 0, i));
}
Debug.Assert(OrderHelper.IsSorted(a));
}
/// <summary>
/// Returns a permutation that gives the elements in the array in ascending order,
/// while not changing the original array a[]</summary>
/// <param name="a">a the array</param>
/// <returns>a permutation <c>p[]</c> such that <c>a[p[0]]</c>, <c>a[p[1]]</c>,
/// ..., <c>a[p[N-1]]</c> are in ascending order</returns>
///
public static int[] IndexSort(int[] a)
{
int N = a.Length;
int[] index = new int[N];
for (int i = 0; i < N; i++)
{
index[i] = i;
}
for (int i = 0; i < N; i++)
{
for (int j = i; j > 0 && OrderHelper.Less(a[index[j]], a[index[j - 1]]); j--)
{
OrderHelper.Exch(index, j, j - 1);
}
}
return(index);
}
// partition the subarray a[lo..hi] so that a[lo..j-1] <= a[j] <= a[j+1..hi]
// and return the index j.
private static int partition(IComparable[] a, int lo, int hi)
{
int i = lo;
int j = hi + 1;
IComparable v = a[lo];
while (true)
{
// find item on lo to swap
while (OrderHelper.Less(a[++i], v))
{
if (i == hi)
{
break;
}
}
// find item on hi to swap
while (OrderHelper.Less(v, a[--j]))
{
if (j == lo)
{
break; // redundant since a[lo] acts as sentinel
}
}
// check if pointers cross
if (i >= j)
{
break;
}
OrderHelper.Exch(a, i, j);
}
// put partitioning item v at a[j]
OrderHelper.Exch(a, lo, j);
// now, a[lo .. j-1] <= a[j] <= a[j+1 .. hi]
return(j);
}
private static void Sort(IComparable[] a, int lo, int hi)
{
int N = hi - lo + 1;
// cutoff to insertion sort
if (N <= CUTOFF)
{
Insertion.Sort(a, lo, hi);
return;
}
// use median-of-3 as partitioning element
else if (N <= 40)
{
int m = median3(a, lo, lo + N / 2, hi);
OrderHelper.Exch(a, m, lo);
}
// use Tukey ninther as partitioning element
else
{
int eps = N / 8;
int mid = lo + N / 2;
int m1 = median3(a, lo, lo + eps, lo + eps + eps);
int m2 = median3(a, mid - eps, mid, mid + eps);
int m3 = median3(a, hi - eps - eps, hi - eps, hi);
int ninther = median3(a, m1, m2, m3);
OrderHelper.Exch(a, ninther, lo);
}
// Bentley-McIlroy 3-way partitioning
int i = lo, j = hi + 1;
int p = lo, q = hi + 1;
IComparable v = a[lo];
while (true)
{
while (OrderHelper.Less(a[++i], v))
{
if (i == hi)
{
break;
}
}
while (OrderHelper.Less(v, a[--j]))
{
if (j == lo)
{
break;
}
}
// pointers cross
if (i == j && OrderHelper.Eq(a[i], v))
{
OrderHelper.Exch(a, ++p, i);
}
if (i >= j)
{
break;
}
OrderHelper.Exch(a, i, j);
if (OrderHelper.Eq(a[i], v))
{
OrderHelper.Exch(a, ++p, i);
}
if (OrderHelper.Eq(a[j], v))
{
OrderHelper.Exch(a, --q, j);
}
}
i = j + 1;
for (int k = lo; k <= p; k++)
{
OrderHelper.Exch(a, k, j--);
}
for (int k = hi; k >= q; k--)
{
OrderHelper.Exch(a, k, i++);
}
Sort(a, lo, j);
Sort(a, i, hi);
}