[Глава 4] Быстрая сортировка

Chapter4_QuickSort/QuickSort.cs

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+static class QuickSort
+{
+    private static readonly Random _rnd = Random.Shared;
+
+    public static List<T> Sort<T>(List<T> source, Comparer<T> comparer)
+    {
+        if (source.Count < 2)
+            return source;
+
+        var referenceIndex = _rnd.Next(source.Count);
+        var reference = source[referenceIndex];
+        var less = new List<T>();
+        var equal = new List<T>();
+        var more = new List<T>();
+
+        for (var i = 0; i < source.Count; i++)
+        {
+            var value = source[i];
+            if (comparer.Compare(value, reference) < 0)
+                less.Add(value);
+            else if (comparer.Compare(value, reference) > 0)
+                more.Add(value);
+            else if (comparer.Compare(value, reference) == 0)
+                equal.Add(value);
+        }
+        less = Sort(less, comparer);
+        more = Sort(more, comparer);
+        var index = 0;
+        foreach (var item in less)
+            source[index++] = item;
+        foreach (var item in equal)
+            source[index++] = item;
+        foreach (var item in more)
+            source[index++] = item;
+        return source;
+    }
+}