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@manofstick
Last active Nov 22, 2018
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What would you like to do?
take ii!
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
namespace ConsoleApp95
{
class Node
{
public Node prev;
public Node next;
public int value;
}
class Program
{
static IEnumerable<int> DataSetRandomSeed42()
{
var r = new Random(42);
for (var i = 0; i < 5_000_000; ++i)
yield return r.Next();
}
static IEnumerable<int> DataSetAscending()
{
for (var i = 0; i < 5_000_000; ++i)
yield return i;
}
static IEnumerable<int> DataSetDescending()
{
for (var i = 0; i < 5_000_000; ++i)
yield return -i;
}
static IEnumerable<int> DataSetAdverserial()
{
for (var i = 0; i < 48; ++i)
yield return int.MaxValue + i;
for (var i = 48; i < 5_000_000; ++i)
yield return -i;
}
static void Main(string[] args)
{
Console.WriteLine($"Environment.Is64BitProcess={Environment.Is64BitProcess}");
Console.WriteLine($"Environment.Version={Environment.Version}");
Console.WriteLine($"Environment.OSVersion={Environment.OSVersion}");
#if true
var sw = Stopwatch.StartNew();
for (var i = 0; i < 10; ++i)
{
sw.Restart();
var sortedTake = SortedTake(DataSetAdverserial(), 50);
Console.WriteLine(sw.ElapsedMilliseconds);
}
#else
for (var i = 0; i < 5; ++i)
{
RunTest(DataSetRandomSeed42, nameof(DataSetRandomSeed42));
RunTest(DataSetAscending, nameof(DataSetAscending));
RunTest(DataSetDescending, nameof(DataSetDescending));
RunTest(DataSetAdverserial, nameof(DataSetAdverserial));
Console.WriteLine();
}
#endif
}
private static void RunTest(Func<IEnumerable<int>> getData, string description)
{
var data = getData();
var sw = Stopwatch.StartNew();
var takeCount = 50;
sw.Restart();
var sortedTake = SortedTake(data, takeCount);
var sortedTakeTime = sw.ElapsedMilliseconds;
sw.Restart();
var linqTake =
data
.OrderBy(i => i)
.Select(i => i)
.Take(takeCount)
.ToList();
var linqTakeTime = sw.ElapsedMilliseconds;
if (!sortedTake.SequenceEqual(linqTake))
throw new Exception("Algo mismatch");
System.Console.WriteLine($"{description}\t{sortedTakeTime}\t{linqTakeTime}\t({(float)sortedTakeTime / linqTakeTime * 100:0.00}%)");
}
private static IList<int> SortedTake(IEnumerable<int> data, int takeCount)
{
var enumerator = data.GetEnumerator();
var initialValues = new List<int>();
while (enumerator.MoveNext() && initialValues.Count < takeCount)
initialValues.Add(enumerator.Current);
initialValues.Sort();
if (initialValues.Count < takeCount)
return initialValues;
var indexes = new List<Node>();
var indexerIndex = takeCount;
Node lastNode = null;
for (var i = takeCount - 1; i >= 0; --i)
{
var node = new Node { prev = lastNode, value = initialValues[i] };
if (lastNode != null)
lastNode.next = node;
if (indexerIndex > i)
{
indexes.Add(node);
indexerIndex = (int)(indexerIndex / 1.55);
}
lastNode = node;
}
while (enumerator.MoveNext())
{
var value = enumerator.Current;
var n = 0;
for (; n < indexes.Count; ++n)
{
if (value >= indexes[n].value)
break;
}
if (n == 0)
continue;
else
{
var insert = indexes[0];
insert.value = value;
if (value >= insert.next.value)
continue;
indexes[0] = insert.next;
insert.next.prev = null;
if (n == indexes.Count)
{
var tail = indexes[indexes.Count - 1];
tail.next = insert;
insert.next = null;
insert.prev = tail;
}
else
{
var search = indexes[n];
while (value >= search.value)
search = search.prev;
insert.next = search.next;
insert.next.prev = insert;
insert.prev = search;
search.next = insert;
}
}
for (--n; n > 0; --n)
indexes[n] = indexes[n].next;
}
var results = new List<int>();
var nn = indexes[indexes.Count - 1];
while (nn != null)
{
results.Add(nn.value);
nn = nn.prev;
}
return results;
}
}
}
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