Add all 23 GoF design pattern implementations (2026-06-13)

03-behavioral/strategy/QuickSort.java

@@ -0,0 +1,26 @@
+package strategy;
+
+public class QuickSort implements SortStrategy {
+    @Override
+    public void sort(int[] data) {
+        System.out.println("  [QuickSort] O(n log n) avg — fast in practice, not stable");
+        quickSort(data, 0, data.length - 1);
+    }
+
+    private void quickSort(int[] a, int lo, int hi) {
+        if (lo >= hi) return;
+        int p = partition(a, lo, hi);
+        quickSort(a, lo, p - 1);
+        quickSort(a, p + 1, hi);
+    }
+
+    private int partition(int[] a, int lo, int hi) {
+        int pivot = a[hi], i = lo;
+        for (int j = lo; j < hi; j++)
+            if (a[j] <= pivot) { int t = a[i]; a[i++] = a[j]; a[j] = t; }
+        int t = a[i]; a[i] = a[hi]; a[hi] = t;
+        return i;
+    }
+
+    @Override public String getName() { return "QuickSort"; }
+}