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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
/*============================================================
**
**
**
**
**
** Purpose: class to sort arrays
**
**
===========================================================*/
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
namespace System.Collections.Generic
{
#region ArraySortHelper for single arrays
internal static class IntrospectiveSortUtilities
{
// This is the threshold where Introspective sort switches to Insertion sort.
// Empirically, 16 seems to speed up most cases without slowing down others, at least for integers.
// Large value types may benefit from a smaller number.
internal const int IntrosortSizeThreshold = 16;
internal static int FloorLog2PlusOne(int n)
{
int result = 0;
while (n >= 1)
{
result++;
n /= 2;
}
return result;
}
[DoesNotReturn]
internal static void ThrowOrIgnoreBadComparer(object? comparer)
{
throw new ArgumentException(SR.Format(SR.Arg_BogusIComparer, comparer));
}
}
internal partial class ArraySortHelper<T>
{
#region IArraySortHelper<T> Members
public void Sort(T[] keys, int index, int length, IComparer<T>? comparer)
{
Debug.Assert(keys != null, "Check the arguments in the caller!");
Debug.Assert(index >= 0 && length >= 0 && (keys.Length - index >= length), "Check the arguments in the caller!");
// Add a try block here to detect IComparers (or their
// underlying IComparables, etc) that are bogus.
try
{
comparer ??= Comparer<T>.Default;
IntrospectiveSort(keys, index, length, comparer.Compare);
}
catch (IndexOutOfRangeException)
{
IntrospectiveSortUtilities.ThrowOrIgnoreBadComparer(comparer);
}
catch (Exception e)
{
throw new InvalidOperationException(SR.InvalidOperation_IComparerFailed, e);
}
}
public int BinarySearch(T[] array, int index, int length, T value, IComparer<T>? comparer)
{
try
{
comparer ??= Comparer<T>.Default;
return InternalBinarySearch(array, index, length, value, comparer);
}
catch (Exception e)
{
throw new InvalidOperationException(SR.InvalidOperation_IComparerFailed, e);
}
}
#endregion
internal static void Sort(T[] keys, int index, int length, Comparison<T> comparer)
{
Debug.Assert(keys != null, "Check the arguments in the caller!");
Debug.Assert(index >= 0 && length >= 0 && (keys.Length - index >= length), "Check the arguments in the caller!");
Debug.Assert(comparer != null, "Check the arguments in the caller!");
// Add a try block here to detect bogus comparisons
try
{
IntrospectiveSort(keys, index, length, comparer);
}
catch (IndexOutOfRangeException)
{
IntrospectiveSortUtilities.ThrowOrIgnoreBadComparer(comparer);
}
catch (Exception e)
{
throw new InvalidOperationException(SR.InvalidOperation_IComparerFailed, e);
}
}
internal static int InternalBinarySearch(T[] array, int index, int length, T value, IComparer<T> comparer)
{
Debug.Assert(array != null, "Check the arguments in the caller!");
Debug.Assert(index >= 0 && length >= 0 && (array.Length - index >= length), "Check the arguments in the caller!");
int lo = index;
int hi = index + length - 1;
while (lo <= hi)
{
int i = lo + ((hi - lo) >> 1);
int order = comparer.Compare(array[i], value);
if (order == 0) return i;
if (order < 0)
{
lo = i + 1;
}
else
{
hi = i - 1;
}
}
return ~lo;
}
private static void SwapIfGreater(T[] keys, Comparison<T> comparer, int a, int b)
{
if (a != b)
{
if (comparer(keys[a], keys[b]) > 0)
{
T key = keys[a];
keys[a] = keys[b];
keys[b] = key;
}
}
}
private static void Swap(T[] a, int i, int j)
{
if (i != j)
{
T t = a[i];
a[i] = a[j];
a[j] = t;
}
}
internal static void IntrospectiveSort(T[] keys, int left, int length, Comparison<T> comparer)
{
Debug.Assert(keys != null);
Debug.Assert(comparer != null);
Debug.Assert(left >= 0);
Debug.Assert(length >= 0);
Debug.Assert(length <= keys.Length);
Debug.Assert(length + left <= keys.Length);
if (length < 2)
return;
IntroSort(keys, left, length + left - 1, 2 * IntrospectiveSortUtilities.FloorLog2PlusOne(length), comparer);
}
private static void IntroSort(T[] keys, int lo, int hi, int depthLimit, Comparison<T> comparer)
{
Debug.Assert(keys != null);
Debug.Assert(comparer != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi < keys.Length);
while (hi > lo)
{
int partitionSize = hi - lo + 1;
if (partitionSize <= IntrospectiveSortUtilities.IntrosortSizeThreshold)
{
if (partitionSize == 1)
{
return;
}
if (partitionSize == 2)
{
SwapIfGreater(keys, comparer, lo, hi);
return;
}
if (partitionSize == 3)
{
SwapIfGreater(keys, comparer, lo, hi - 1);
SwapIfGreater(keys, comparer, lo, hi);
SwapIfGreater(keys, comparer, hi - 1, hi);
return;
}
InsertionSort(keys, lo, hi, comparer);
return;
}
if (depthLimit == 0)
{
Heapsort(keys, lo, hi, comparer);
return;
}
depthLimit--;
int p = PickPivotAndPartition(keys, lo, hi, comparer);
// Note we've already partitioned around the pivot and do not have to move the pivot again.
IntroSort(keys, p + 1, hi, depthLimit, comparer);
hi = p - 1;
}
}
private static int PickPivotAndPartition(T[] keys, int lo, int hi, Comparison<T> comparer)
{
Debug.Assert(keys != null);
Debug.Assert(comparer != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi > lo);
Debug.Assert(hi < keys.Length);
// Compute median-of-three. But also partition them, since we've done the comparison.
int middle = lo + ((hi - lo) / 2);
// Sort lo, mid and hi appropriately, then pick mid as the pivot.
SwapIfGreater(keys, comparer, lo, middle); // swap the low with the mid point
SwapIfGreater(keys, comparer, lo, hi); // swap the low with the high
SwapIfGreater(keys, comparer, middle, hi); // swap the middle with the high
T pivot = keys[middle];
Swap(keys, middle, hi - 1);
int left = lo, right = hi - 1; // We already partitioned lo and hi and put the pivot in hi - 1. And we pre-increment & decrement below.
while (left < right)
{
while (comparer(keys[++left], pivot) < 0) ;
while (comparer(pivot, keys[--right]) < 0) ;
if (left >= right)
break;
Swap(keys, left, right);
}
// Put pivot in the right location.
Swap(keys, left, (hi - 1));
return left;
}
private static void Heapsort(T[] keys, int lo, int hi, Comparison<T> comparer)
{
Debug.Assert(keys != null);
Debug.Assert(comparer != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi > lo);
Debug.Assert(hi < keys.Length);
int n = hi - lo + 1;
for (int i = n / 2; i >= 1; i--)
{
DownHeap(keys, i, n, lo, comparer);
}
for (int i = n; i > 1; i--)
{
Swap(keys, lo, lo + i - 1);
DownHeap(keys, 1, i - 1, lo, comparer);
}
}
private static void DownHeap(T[] keys, int i, int n, int lo, Comparison<T> comparer)
{
Debug.Assert(keys != null);
Debug.Assert(comparer != null);
Debug.Assert(lo >= 0);
Debug.Assert(lo < keys.Length);
T d = keys[lo + i - 1];
int child;
while (i <= n / 2)
{
child = 2 * i;
if (child < n && comparer(keys[lo + child - 1], keys[lo + child]) < 0)
{
child++;
}
if (!(comparer(d, keys[lo + child - 1]) < 0))
break;
keys[lo + i - 1] = keys[lo + child - 1];
i = child;
}
keys[lo + i - 1] = d;
}
private static void InsertionSort(T[] keys, int lo, int hi, Comparison<T> comparer)
{
Debug.Assert(keys != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi >= lo);
Debug.Assert(hi <= keys.Length);
int i, j;
T t;
for (i = lo; i < hi; i++)
{
j = i;
t = keys[i + 1];
while (j >= lo && comparer(t, keys[j]) < 0)
{
keys[j + 1] = keys[j];
j--;
}
keys[j + 1] = t;
}
}
}
internal partial class GenericArraySortHelper<T>
where T : IComparable<T>
{
// Do not add a constructor to this class because ArraySortHelper<T>.CreateSortHelper will not execute it
#region IArraySortHelper<T> Members
public void Sort(T[] keys, int index, int length, IComparer<T>? comparer)
{
Debug.Assert(keys != null, "Check the arguments in the caller!");
Debug.Assert(index >= 0 && length >= 0 && (keys.Length - index >= length), "Check the arguments in the caller!");
try
{
if (comparer == null || comparer == Comparer<T>.Default)
{
IntrospectiveSort(keys, index, length);
}
else
{
ArraySortHelper<T>.IntrospectiveSort(keys, index, length, comparer.Compare);
}
}
catch (IndexOutOfRangeException)
{
IntrospectiveSortUtilities.ThrowOrIgnoreBadComparer(comparer);
}
catch (Exception e)
{
throw new InvalidOperationException(SR.InvalidOperation_IComparerFailed, e);
}
}
public int BinarySearch(T[] array, int index, int length, T value, IComparer<T>? comparer)
{
Debug.Assert(array != null, "Check the arguments in the caller!");
Debug.Assert(index >= 0 && length >= 0 && (array.Length - index >= length), "Check the arguments in the caller!");
try
{
if (comparer == null || comparer == Comparer<T>.Default)
{
return BinarySearch(array, index, length, value);
}
else
{
return ArraySortHelper<T>.InternalBinarySearch(array, index, length, value, comparer);
}
}
catch (Exception e)
{
throw new InvalidOperationException(SR.InvalidOperation_IComparerFailed, e);
}
}
#endregion
// This function is called when the user doesn't specify any comparer.
// Since T is constrained here, we can call IComparable<T>.CompareTo here.
// We can avoid boxing for value type and casting for reference types.
private static int BinarySearch(T[] array, int index, int length, T value)
{
int lo = index;
int hi = index + length - 1;
while (lo <= hi)
{
int i = lo + ((hi - lo) >> 1);
int order;
if (array[i] == null)
{
order = (value == null) ? 0 : -1;
}
else
{
order = array[i].CompareTo(value);
}
if (order == 0)
{
return i;
}
if (order < 0)
{
lo = i + 1;
}
else
{
hi = i - 1;
}
}
return ~lo;
}
private static void SwapIfGreaterWithItems(T[] keys, int a, int b)
{
Debug.Assert(keys != null);
Debug.Assert(0 <= a && a < keys.Length);
Debug.Assert(0 <= b && b < keys.Length);
if (a != b)
{
if (keys[a] != null && keys[a].CompareTo(keys[b]) > 0)
{
T key = keys[a];
keys[a] = keys[b];
keys[b] = key;
}
}
}
private static void Swap(T[] a, int i, int j)
{
if (i != j)
{
T t = a[i];
a[i] = a[j];
a[j] = t;
}
}
internal static void IntrospectiveSort(T[] keys, int left, int length)
{
Debug.Assert(keys != null);
Debug.Assert(left >= 0);
Debug.Assert(length >= 0);
Debug.Assert(length <= keys.Length);
Debug.Assert(length + left <= keys.Length);
if (length < 2)
return;
IntroSort(keys, left, length + left - 1, 2 * IntrospectiveSortUtilities.FloorLog2PlusOne(length));
}
private static void IntroSort(T[] keys, int lo, int hi, int depthLimit)
{
Debug.Assert(keys != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi < keys.Length);
while (hi > lo)
{
int partitionSize = hi - lo + 1;
if (partitionSize <= IntrospectiveSortUtilities.IntrosortSizeThreshold)
{
if (partitionSize == 1)
{
return;
}
if (partitionSize == 2)
{
SwapIfGreaterWithItems(keys, lo, hi);
return;
}
if (partitionSize == 3)
{
SwapIfGreaterWithItems(keys, lo, hi - 1);
SwapIfGreaterWithItems(keys, lo, hi);
SwapIfGreaterWithItems(keys, hi - 1, hi);
return;
}
InsertionSort(keys, lo, hi);
return;
}
if (depthLimit == 0)
{
Heapsort(keys, lo, hi);
return;
}
depthLimit--;
int p = PickPivotAndPartition(keys, lo, hi);
// Note we've already partitioned around the pivot and do not have to move the pivot again.
IntroSort(keys, p + 1, hi, depthLimit);
hi = p - 1;
}
}
private static int PickPivotAndPartition(T[] keys, int lo, int hi)
{
Debug.Assert(keys != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi > lo);
Debug.Assert(hi < keys.Length);
// Compute median-of-three. But also partition them, since we've done the comparison.
int middle = lo + ((hi - lo) / 2);
// Sort lo, mid and hi appropriately, then pick mid as the pivot.
SwapIfGreaterWithItems(keys, lo, middle); // swap the low with the mid point
SwapIfGreaterWithItems(keys, lo, hi); // swap the low with the high
SwapIfGreaterWithItems(keys, middle, hi); // swap the middle with the high
T pivot = keys[middle];
Swap(keys, middle, hi - 1);
int left = lo, right = hi - 1; // We already partitioned lo and hi and put the pivot in hi - 1. And we pre-increment & decrement below.
while (left < right)
{
if (pivot == null)
{
while (left < (hi - 1) && keys[++left] == null) ;
while (right > lo && keys[--right] != null) ;
}
else
{
while (pivot.CompareTo(keys[++left]) > 0) ;
while (pivot.CompareTo(keys[--right]) < 0) ;
}
if (left >= right)
break;
Swap(keys, left, right);
}
// Put pivot in the right location.
Swap(keys, left, (hi - 1));
return left;
}
private static void Heapsort(T[] keys, int lo, int hi)
{
Debug.Assert(keys != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi > lo);
Debug.Assert(hi < keys.Length);
int n = hi - lo + 1;
for (int i = n / 2; i >= 1; i--)
{
DownHeap(keys, i, n, lo);
}
for (int i = n; i > 1; i--)
{
Swap(keys, lo, lo + i - 1);
DownHeap(keys, 1, i - 1, lo);
}
}
private static void DownHeap(T[] keys, int i, int n, int lo)
{
Debug.Assert(keys != null);
Debug.Assert(lo >= 0);
Debug.Assert(lo < keys.Length);
T d = keys[lo + i - 1];
int child;
while (i <= n / 2)
{
child = 2 * i;
if (child < n && (keys[lo + child - 1] == null || keys[lo + child - 1].CompareTo(keys[lo + child]) < 0))
{
child++;
}
if (keys[lo + child - 1] == null || keys[lo + child - 1].CompareTo(d) < 0)
break;
keys[lo + i - 1] = keys[lo + child - 1];
i = child;
}
keys[lo + i - 1] = d;
}
private static void InsertionSort(T[] keys, int lo, int hi)
{
Debug.Assert(keys != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi >= lo);
Debug.Assert(hi <= keys.Length);
int i, j;
T t;
for (i = lo; i < hi; i++)
{
j = i;
t = keys[i + 1];
while (j >= lo && (t == null || t.CompareTo(keys[j]) < 0))
{
keys[j + 1] = keys[j];
j--;
}
keys[j + 1] = t;
}
}
}
#endregion
#region ArraySortHelper for paired key and value arrays
internal partial class ArraySortHelper<TKey, TValue>
{
public void Sort(TKey[] keys, TValue[] values, int index, int length, IComparer<TKey>? comparer)
{
Debug.Assert(keys != null, "Check the arguments in the caller!"); // Precondition on interface method
Debug.Assert(values != null, "Check the arguments in the caller!");
Debug.Assert(index >= 0 && length >= 0 && (keys.Length - index >= length), "Check the arguments in the caller!");
// Add a try block here to detect IComparers (or their
// underlying IComparables, etc) that are bogus.
try
{
if (comparer == null || comparer == Comparer<TKey>.Default)
{
comparer = Comparer<TKey>.Default;
}
IntrospectiveSort(keys, values, index, length, comparer);
}
catch (IndexOutOfRangeException)
{
IntrospectiveSortUtilities.ThrowOrIgnoreBadComparer(comparer);
}
catch (Exception e)
{
throw new InvalidOperationException(SR.InvalidOperation_IComparerFailed, e);
}
}
private static void SwapIfGreaterWithItems(TKey[] keys, TValue[] values, IComparer<TKey> comparer, int a, int b)
{
Debug.Assert(keys != null);
Debug.Assert(values != null);
Debug.Assert(comparer != null);
Debug.Assert(0 <= a && a < keys.Length && a < values.Length);
Debug.Assert(0 <= b && b < keys.Length && b < values.Length);
if (a != b)
{
if (comparer.Compare(keys[a], keys[b]) > 0)
{
TKey key = keys[a];
keys[a] = keys[b];
keys[b] = key;
TValue value = values[a];
values[a] = values[b];
values[b] = value;
}
}
}
private static void Swap(TKey[] keys, TValue[] values, int i, int j)
{
if (i != j)
{
TKey k = keys[i];
keys[i] = keys[j];
keys[j] = k;
TValue v = values[i];
values[i] = values[j];
values[j] = v;
}
}
internal static void IntrospectiveSort(TKey[] keys, TValue[] values, int left, int length, IComparer<TKey> comparer)
{
Debug.Assert(keys != null);
Debug.Assert(values != null);
Debug.Assert(comparer != null);
Debug.Assert(left >= 0);
Debug.Assert(length >= 0);
Debug.Assert(length <= keys.Length);
Debug.Assert(length + left <= keys.Length);
Debug.Assert(length + left <= values.Length);
if (length < 2)
return;
IntroSort(keys, values, left, length + left - 1, 2 * IntrospectiveSortUtilities.FloorLog2PlusOne(length), comparer);
}
private static void IntroSort(TKey[] keys, TValue[] values, int lo, int hi, int depthLimit, IComparer<TKey> comparer)
{
Debug.Assert(keys != null);
Debug.Assert(values != null);
Debug.Assert(comparer != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi < keys.Length);
while (hi > lo)
{
int partitionSize = hi - lo + 1;
if (partitionSize <= IntrospectiveSortUtilities.IntrosortSizeThreshold)
{
if (partitionSize == 1)
{
return;
}
if (partitionSize == 2)
{
SwapIfGreaterWithItems(keys, values, comparer, lo, hi);
return;
}
if (partitionSize == 3)
{
SwapIfGreaterWithItems(keys, values, comparer, lo, hi - 1);
SwapIfGreaterWithItems(keys, values, comparer, lo, hi);
SwapIfGreaterWithItems(keys, values, comparer, hi - 1, hi);
return;
}
InsertionSort(keys, values, lo, hi, comparer);
return;
}
if (depthLimit == 0)
{
Heapsort(keys, values, lo, hi, comparer);
return;
}
depthLimit--;
int p = PickPivotAndPartition(keys, values, lo, hi, comparer);
// Note we've already partitioned around the pivot and do not have to move the pivot again.
IntroSort(keys, values, p + 1, hi, depthLimit, comparer);
hi = p - 1;
}
}
private static int PickPivotAndPartition(TKey[] keys, TValue[] values, int lo, int hi, IComparer<TKey> comparer)
{
Debug.Assert(keys != null);
Debug.Assert(values != null);
Debug.Assert(comparer != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi > lo);
Debug.Assert(hi < keys.Length);
// Compute median-of-three. But also partition them, since we've done the comparison.
int middle = lo + ((hi - lo) / 2);
// Sort lo, mid and hi appropriately, then pick mid as the pivot.
SwapIfGreaterWithItems(keys, values, comparer, lo, middle); // swap the low with the mid point
SwapIfGreaterWithItems(keys, values, comparer, lo, hi); // swap the low with the high
SwapIfGreaterWithItems(keys, values, comparer, middle, hi); // swap the middle with the high
TKey pivot = keys[middle];
Swap(keys, values, middle, hi - 1);
int left = lo, right = hi - 1; // We already partitioned lo and hi and put the pivot in hi - 1. And we pre-increment & decrement below.
while (left < right)
{
while (comparer.Compare(keys[++left], pivot) < 0) ;
while (comparer.Compare(pivot, keys[--right]) < 0) ;
if (left >= right)
break;
Swap(keys, values, left, right);
}
// Put pivot in the right location.
Swap(keys, values, left, (hi - 1));
return left;
}
private static void Heapsort(TKey[] keys, TValue[] values, int lo, int hi, IComparer<TKey> comparer)
{
Debug.Assert(keys != null);
Debug.Assert(values != null);
Debug.Assert(comparer != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi > lo);
Debug.Assert(hi < keys.Length);
int n = hi - lo + 1;
for (int i = n / 2; i >= 1; i--)
{
DownHeap(keys, values, i, n, lo, comparer);
}
for (int i = n; i > 1; i--)
{
Swap(keys, values, lo, lo + i - 1);
DownHeap(keys, values, 1, i - 1, lo, comparer);
}
}
private static void DownHeap(TKey[] keys, TValue[] values, int i, int n, int lo, IComparer<TKey> comparer)
{
Debug.Assert(keys != null);
Debug.Assert(values != null);
Debug.Assert(comparer != null);
Debug.Assert(lo >= 0);
Debug.Assert(lo < keys.Length);
TKey d = keys[lo + i - 1];
TValue dValue = values[lo + i - 1];
int child;
while (i <= n / 2)
{
child = 2 * i;
if (child < n && comparer.Compare(keys[lo + child - 1], keys[lo + child]) < 0)
{
child++;
}
if (!(comparer.Compare(d, keys[lo + child - 1]) < 0))
break;
keys[lo + i - 1] = keys[lo + child - 1];
values[lo + i - 1] = values[lo + child - 1];
i = child;
}
keys[lo + i - 1] = d;
values[lo + i - 1] = dValue;
}
private static void InsertionSort(TKey[] keys, TValue[] values, int lo, int hi, IComparer<TKey> comparer)
{
Debug.Assert(keys != null);
Debug.Assert(values != null);
Debug.Assert(comparer != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi >= lo);
Debug.Assert(hi <= keys.Length);
int i, j;
TKey t;
TValue tValue;
for (i = lo; i < hi; i++)
{
j = i;
t = keys[i + 1];
tValue = values[i + 1];
while (j >= lo && comparer.Compare(t, keys[j]) < 0)
{
keys[j + 1] = keys[j];
values[j + 1] = values[j];
j--;
}
keys[j + 1] = t;
values[j + 1] = tValue;
}
}
}
internal partial class GenericArraySortHelper<TKey, TValue>
where TKey : IComparable<TKey>
{
public void Sort(TKey[] keys, TValue[] values, int index, int length, IComparer<TKey>? comparer)
{
Debug.Assert(keys != null, "Check the arguments in the caller!");
Debug.Assert(index >= 0 && length >= 0 && (keys.Length - index >= length), "Check the arguments in the caller!");
// Add a try block here to detect IComparers (or their
// underlying IComparables, etc) that are bogus.
try
{
if (comparer == null || comparer == Comparer<TKey>.Default)
{
IntrospectiveSort(keys, values, index, length);
}
else
{
ArraySortHelper<TKey, TValue>.IntrospectiveSort(keys, values, index, length, comparer);
}
}
catch (IndexOutOfRangeException)
{
IntrospectiveSortUtilities.ThrowOrIgnoreBadComparer(comparer);
}
catch (Exception e)
{
throw new InvalidOperationException(SR.InvalidOperation_IComparerFailed, e);
}
}
private static void SwapIfGreaterWithItems(TKey[] keys, TValue[] values, int a, int b)
{
if (a != b)
{
if (keys[a] != null && keys[a].CompareTo(keys[b]) > 0)
{
TKey key = keys[a];
keys[a] = keys[b];
keys[b] = key;
TValue value = values[a];
values[a] = values[b];
values[b] = value;
}
}
}
private static void Swap(TKey[] keys, TValue[] values, int i, int j)
{
if (i != j)
{
TKey k = keys[i];
keys[i] = keys[j];
keys[j] = k;
TValue v = values[i];
values[i] = values[j];
values[j] = v;
}
}
internal static void IntrospectiveSort(TKey[] keys, TValue[] values, int left, int length)
{
Debug.Assert(keys != null);
Debug.Assert(values != null);
Debug.Assert(left >= 0);
Debug.Assert(length >= 0);
Debug.Assert(length <= keys.Length);
Debug.Assert(length + left <= keys.Length);
Debug.Assert(length + left <= values.Length);
if (length < 2)
return;
IntroSort(keys, values, left, length + left - 1, 2 * IntrospectiveSortUtilities.FloorLog2PlusOne(length));
}
private static void IntroSort(TKey[] keys, TValue[] values, int lo, int hi, int depthLimit)
{
Debug.Assert(keys != null);
Debug.Assert(values != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi < keys.Length);
while (hi > lo)
{
int partitionSize = hi - lo + 1;
if (partitionSize <= IntrospectiveSortUtilities.IntrosortSizeThreshold)
{
if (partitionSize == 1)
{
return;
}
if (partitionSize == 2)
{
SwapIfGreaterWithItems(keys, values, lo, hi);
return;
}
if (partitionSize == 3)
{
SwapIfGreaterWithItems(keys, values, lo, hi - 1);
SwapIfGreaterWithItems(keys, values, lo, hi);
SwapIfGreaterWithItems(keys, values, hi - 1, hi);
return;
}
InsertionSort(keys, values, lo, hi);
return;
}
if (depthLimit == 0)
{
Heapsort(keys, values, lo, hi);
return;
}
depthLimit--;
int p = PickPivotAndPartition(keys, values, lo, hi);
// Note we've already partitioned around the pivot and do not have to move the pivot again.
IntroSort(keys, values, p + 1, hi, depthLimit);
hi = p - 1;
}
}
private static int PickPivotAndPartition(TKey[] keys, TValue[] values, int lo, int hi)
{
Debug.Assert(keys != null);
Debug.Assert(values != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi > lo);
Debug.Assert(hi < keys.Length);
// Compute median-of-three. But also partition them, since we've done the comparison.
int middle = lo + ((hi - lo) / 2);
// Sort lo, mid and hi appropriately, then pick mid as the pivot.
SwapIfGreaterWithItems(keys, values, lo, middle); // swap the low with the mid point
SwapIfGreaterWithItems(keys, values, lo, hi); // swap the low with the high
SwapIfGreaterWithItems(keys, values, middle, hi); // swap the middle with the high
TKey pivot = keys[middle];
Swap(keys, values, middle, hi - 1);
int left = lo, right = hi - 1; // We already partitioned lo and hi and put the pivot in hi - 1. And we pre-increment & decrement below.
while (left < right)
{
if (pivot == null)
{
while (left < (hi - 1) && keys[++left] == null) ;
while (right > lo && keys[--right] != null) ;
}
else
{
while (pivot.CompareTo(keys[++left]) > 0) ;
while (pivot.CompareTo(keys[--right]) < 0) ;
}
if (left >= right)
break;
Swap(keys, values, left, right);
}
// Put pivot in the right location.
Swap(keys, values, left, (hi - 1));
return left;
}
private static void Heapsort(TKey[] keys, TValue[] values, int lo, int hi)
{
Debug.Assert(keys != null);
Debug.Assert(values != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi > lo);
Debug.Assert(hi < keys.Length);
int n = hi - lo + 1;
for (int i = n / 2; i >= 1; i--)
{
DownHeap(keys, values, i, n, lo);
}
for (int i = n; i > 1; i--)
{
Swap(keys, values, lo, lo + i - 1);
DownHeap(keys, values, 1, i - 1, lo);
}
}
private static void DownHeap(TKey[] keys, TValue[] values, int i, int n, int lo)
{
Debug.Assert(keys != null);
Debug.Assert(lo >= 0);
Debug.Assert(lo < keys.Length);
TKey d = keys[lo + i - 1];
TValue dValue = values[lo + i - 1];
int child;
while (i <= n / 2)
{
child = 2 * i;
if (child < n && (keys[lo + child - 1] == null || keys[lo + child - 1].CompareTo(keys[lo + child]) < 0))
{
child++;
}
if (keys[lo + child - 1] == null || keys[lo + child - 1].CompareTo(d) < 0)
break;
keys[lo + i - 1] = keys[lo + child - 1];
values[lo + i - 1] = values[lo + child - 1];
i = child;
}
keys[lo + i - 1] = d;
values[lo + i - 1] = dValue;
}
private static void InsertionSort(TKey[] keys, TValue[] values, int lo, int hi)
{
Debug.Assert(keys != null);
Debug.Assert(values != null);
Debug.Assert(lo >= 0);
Debug.Assert(hi >= lo);
Debug.Assert(hi <= keys.Length);
int i, j;
TKey t;
TValue tValue;
for (i = lo; i < hi; i++)
{
j = i;
t = keys[i + 1];
tValue = values[i + 1];
while (j >= lo && (t == null || t.CompareTo(keys[j]) < 0))
{
keys[j + 1] = keys[j];
values[j + 1] = values[j];
j--;
}
keys[j + 1] = t;
values[j + 1] = tValue;
}
}
}
#endregion
}
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