Adding algorithms and datastructures

tests/test_randomized_algorithm.py

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+"""
+Unit tests for randomized selection algorithm.
+
+Author: Carlos Gutierrez
+Course: MSCS532 - Data Structures and Algorithms
+"""
+
+import pytest
+from src.randomized_algorithm import randomized_select, find_median
+
+
+class TestRandomizedSelect:
+    """Test cases for randomized_select function."""
+    
+    def test_basic_selection(self):
+        """Test basic selection operations."""
+        arr = [3, 1, 4, 1, 5, 9, 2, 6]
+        assert randomized_select(arr, 1, seed=42) == 1
+        assert randomized_select(arr, 2, seed=42) == 1
+        assert randomized_select(arr, 3, seed=42) == 2
+        assert randomized_select(arr, 4, seed=42) == 3
+        assert randomized_select(arr, len(arr), seed=42) == 9
+    
+    def test_sorted_array(self):
+        """Test on sorted array."""
+        arr = list(range(1, 11))
+        for i in range(1, 11):
+            assert randomized_select(arr, i, seed=42) == i
+    
+    def test_reverse_sorted_array(self):
+        """Test on reverse-sorted array."""
+        arr = list(range(10, 0, -1))
+        for i in range(1, 11):
+            assert randomized_select(arr, i, seed=42) == i
+    
+    def test_duplicate_elements(self):
+        """Test with duplicate elements."""
+        arr = [5, 5, 5, 3, 3, 1, 1, 1]
+        assert randomized_select(arr, 1, seed=42) == 1
+        assert randomized_select(arr, 2, seed=42) == 1
+        assert randomized_select(arr, 3, seed=42) == 1
+        assert randomized_select(arr, 4, seed=42) == 3
+        assert randomized_select(arr, 5, seed=42) == 3
+        assert randomized_select(arr, 6, seed=42) == 5
+    
+    def test_single_element(self):
+        """Test with single element."""
+        arr = [42]
+        assert randomized_select(arr, 1, seed=42) == 42
+    
+    def test_empty_array(self):
+        """Test with empty array."""
+        with pytest.raises(IndexError):
+            randomized_select([], 1)
+    
+    def test_invalid_k(self):
+        """Test with invalid k values."""
+        arr = [1, 2, 3]
+        with pytest.raises(ValueError):
+            randomized_select(arr, 0)
+        with pytest.raises(ValueError):
+            randomized_select(arr, 4)
+    
+    def test_key_function(self):
+        """Test with custom key function."""
+        arr = [{'value': 3}, {'value': 1}, {'value': 2}]
+        result = randomized_select(arr, 2, key=lambda x: x['value'], seed=42)
+        assert result['value'] == 2
+    
+    def test_large_array(self):
+        """Test with larger array."""
+        arr = list(range(100, 0, -1))
+        assert randomized_select(arr, 50, seed=42) == 50
+        assert randomized_select(arr, 1, seed=42) == 1
+        assert randomized_select(arr, 100, seed=42) == 100
+    
+    def test_reproducibility(self):
+        """Test that results are reproducible with same seed."""
+        arr = [3, 1, 4, 1, 5, 9, 2, 6]
+        result1 = randomized_select(arr, 4, seed=42)
+        result2 = randomized_select(arr, 4, seed=42)
+        assert result1 == result2
+
+
+class TestFindMedian:
+    """Test cases for find_median function."""
+    
+    def test_odd_length(self):
+        """Test median of odd-length array."""
+        arr = [3, 1, 4, 1, 5]
+        assert find_median(arr, seed=42) == 3
+    
+    def test_even_length(self):
+        """Test median of even-length array (returns lower median)."""
+        arr = [3, 1, 4, 1, 5, 9]
+        assert find_median(arr, seed=42) == 3
+    
+    def test_sorted_array(self):
+        """Test median of sorted array."""
+        arr = list(range(1, 11))
+        assert find_median(arr, seed=42) == 5
+    
+    def test_empty_array(self):
+        """Test median of empty array."""
+        with pytest.raises(ValueError):
+            find_median([])
+