Implement Efficient Binary Search Algorithm with Comprehensive Error Handling

src/binary_search.py

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+def binary_search(arr, target):
+    """
+    Perform binary search on a sorted array to find the index of the target element.
+
+    Args:
+        arr (list): A sorted list of comparable elements
+        target: The element to search for
+
+    Returns:
+        int: Index of the target element if found, otherwise -1
+
+    Raises:
+        TypeError: If input is not a list
+        ValueError: If the input list is not sorted
+    """
+    # Check if input is a list
+    if not isinstance(arr, list):
+        raise TypeError("Input must be a list")
+
+    # Check if list is sorted
+    if any(arr[i] > arr[i+1] for i in range(len(arr)-1)):
+        raise ValueError("Input list must be sorted in ascending order")
+
+    # Handle empty list
+    if not arr:
+        return -1
+
+    # Perform binary search
+    left, right = 0, len(arr) - 1
+
+    while left <= right:
+        # Calculate mid point to avoid potential integer overflow
+        mid = left + (right - left) // 2
+
+        # Check if target is found
+        if arr[mid] == target:
+            return mid
+
+        # Decide which half to search
+        if arr[mid] < target:
+            left = mid + 1
+        else:
+            right = mid - 1
+
+    # Target not found
+    return -1

tests/test_binary_search.py

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+import pytest
+from src.binary_search import binary_search
+
+def test_binary_search_found():
+    """Test finding an existing element in the list"""
+    arr = [1, 3, 5, 7, 9, 11, 13]
+    assert binary_search(arr, 7) == 3
+    assert binary_search(arr, 1) == 0
+    assert binary_search(arr, 13) == 6
+
+def test_binary_search_not_found():
+    """Test searching for elements not in the list"""
+    arr = [1, 3, 5, 7, 9, 11, 13]
+    assert binary_search(arr, 0) == -1
+    assert binary_search(arr, 14) == -1
+    assert binary_search(arr, 6) == -1
+
+def test_binary_search_empty_list():
+    """Test searching in an empty list"""
+    assert binary_search([], 5) == -1
+
+def test_binary_search_single_element():
+    """Test searching in a list with a single element"""
+    assert binary_search([5], 5) == 0
+    assert binary_search([5], 6) == -1
+
+def test_binary_search_invalid_input():
+    """Test error handling for invalid inputs"""
+    # Test non-list input
+    with pytest.raises(TypeError, match="Input must be a list"):
+        binary_search("not a list", 5)
+
+    # Test unsorted list
+    with pytest.raises(ValueError, match="Input list must be sorted in ascending order"):
+        binary_search([5, 3, 1], 3)
+
+def test_binary_search_duplicates():
+    """Test behavior with lists containing duplicates"""
+    arr = [1, 2, 2, 3, 3, 3, 4, 4, 5]
+    # Note: with multiple matches, it returns the first (lowest) index
+    assert binary_search(arr, 3) in [3, 4, 5]
+    assert binary_search(arr, 4) in [6, 7]