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examples/quicksort_demo.py

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+"""
+Demonstration of Quicksort algorithm usage.
+"""
+
+import sys
+import os
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), '..')))
+
+from src.quicksort import quicksort, randomized_quicksort, quicksort_3way
+
+
+def demo_basic_quicksort():
+    """Demonstrate basic Quicksort usage."""
+    print("=" * 60)
+    print("BASIC QUICKSORT DEMONSTRATION")
+    print("=" * 60)
+    
+    # Example 1: Simple integer array
+    print("\n1. Sorting a simple integer array:")
+    arr = [64, 34, 25, 12, 22, 11, 90]
+    print(f"   Original: {arr}")
+    quicksort(arr)
+    print(f"   Sorted:   {arr}")
+    
+    # Example 2: Already sorted array
+    print("\n2. Sorting an already sorted array:")
+    arr = [1, 2, 3, 4, 5]
+    print(f"   Original: {arr}")
+    quicksort(arr)
+    print(f"   Sorted:   {arr}")
+    
+    # Example 3: Reverse sorted array
+    print("\n3. Sorting a reverse-sorted array:")
+    arr = [5, 4, 3, 2, 1]
+    print(f"   Original: {arr}")
+    quicksort(arr)
+    print(f"   Sorted:   {arr}")
+    
+    # Example 4: Array with duplicates
+    print("\n4. Sorting an array with duplicate elements:")
+    arr = [5, 2, 8, 2, 9, 1, 5, 5]
+    print(f"   Original: {arr}")
+    quicksort(arr)
+    print(f"   Sorted:   {arr}")
+    
+    # Example 5: Non-in-place sorting
+    print("\n5. Non-in-place sorting (preserves original):")
+    arr = [3, 1, 4, 1, 5, 9, 2, 6]
+    original = arr.copy()
+    sorted_arr = quicksort(arr, in_place=False)
+    print(f"   Original: {original}")
+    print(f"   Sorted:   {sorted_arr}")
+    print(f"   Original unchanged: {arr == original}")
+
+
+def demo_randomized_quicksort():
+    """Demonstrate Randomized Quicksort usage."""
+    print("\n" + "=" * 60)
+    print("RANDOMIZED QUICKSORT DEMONSTRATION")
+    print("=" * 60)
+    
+    # Example 1: Random array
+    print("\n1. Sorting a random array:")
+    arr = [64, 34, 25, 12, 22, 11, 90]
+    print(f"   Original: {arr}")
+    randomized_quicksort(arr, seed=42)
+    print(f"   Sorted:   {arr}")
+    
+    # Example 2: Sorted array (randomized should handle better)
+    print("\n2. Sorting a sorted array (worst case for deterministic):")
+    arr = list(range(1, 11))
+    print(f"   Original: {arr}")
+    randomized_quicksort(arr, seed=42)
+    print(f"   Sorted:   {arr}")
+    
+    # Example 3: Reproducibility with seed
+    print("\n3. Reproducibility with same seed:")
+    arr1 = [5, 2, 8, 1, 9, 3, 7, 4, 6]
+    arr2 = arr1.copy()
+    randomized_quicksort(arr1, seed=42)
+    randomized_quicksort(arr2, seed=42)
+    print(f"   Array 1: {arr1}")
+    print(f"   Array 2: {arr2}")
+    print(f"   Results match: {arr1 == arr2}")
+
+
+def demo_3way_quicksort():
+    """Demonstrate Three-way Quicksort usage."""
+    print("\n" + "=" * 60)
+    print("THREE-WAY QUICKSORT DEMONSTRATION")
+    print("=" * 60)
+    
+    # Example 1: Array with many duplicates
+    print("\n1. Sorting array with many duplicate elements:")
+    arr = [3, 2, 3, 1, 3, 2, 1, 3, 2, 1]
+    print(f"   Original: {arr}")
+    quicksort_3way(arr)
+    print(f"   Sorted:   {arr}")
+    
+    # Example 2: All same elements
+    print("\n2. Sorting array with all same elements:")
+    arr = [5, 5, 5, 5, 5]
+    print(f"   Original: {arr}")
+    quicksort_3way(arr)
+    print(f"   Sorted:   {arr}")
+    
+    # Example 3: Random array
+    print("\n3. Sorting a random array:")
+    arr = [64, 34, 25, 12, 22, 11, 90]
+    print(f"   Original: {arr}")
+    quicksort_3way(arr)
+    print(f"   Sorted:   {arr}")
+
+
+def demo_custom_key():
+    """Demonstrate sorting with custom key function."""
+    print("\n" + "=" * 60)
+    print("CUSTOM KEY FUNCTION DEMONSTRATION")
+    print("=" * 60)
+    
+    # Example 1: Sorting dictionaries
+    print("\n1. Sorting list of dictionaries by value:")
+    arr = [
+        {'name': 'Alice', 'age': 30},
+        {'name': 'Bob', 'age': 25},
+        {'name': 'Charlie', 'age': 35}
+    ]
+    print(f"   Original: {arr}")
+    quicksort(arr, key=lambda x: x['age'])
+    print(f"   Sorted by age: {arr}")
+    
+    # Example 2: Sorting tuples
+    print("\n2. Sorting list of tuples by second element:")
+    arr = [('apple', 3), ('banana', 1), ('cherry', 2)]
+    print(f"   Original: {arr}")
+    quicksort(arr, key=lambda x: x[1])
+    print(f"   Sorted by count: {arr}")
+
+
+if __name__ == '__main__':
+    demo_basic_quicksort()
+    demo_randomized_quicksort()
+    demo_3way_quicksort()
+    demo_custom_key()
+    
+    print("\n" + "=" * 60)
+    print("DEMONSTRATION COMPLETE")
+    print("=" * 60)
+