Implement Efficient Binary Search Algorithm with Comprehensive Testing

src/binary_search.py

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+def binary_search(arr, target):
+    """
+    Perform binary search on a sorted array to find the target element.
+
+    Args:
+        arr (list): A sorted list of comparable elements.
+        target: The element to search for in the array.
+
+    Returns:
+        int: The index of the target element if found, -1 otherwise.
+
+    Raises:
+        TypeError: If the input is not a list.
+        ValueError: If the input list is not sorted.
+    """
+    # Validate input
+    if not isinstance(arr, list):
+        raise TypeError("Input must be a list")
+
+    # Check if the list is sorted
+    if not all(arr[i] <= arr[i+1] for i in range(len(arr)-1)):
+        raise ValueError("Input list must be sorted in ascending order")
+
+    # Binary search implementation
+    left, right = 0, len(arr) - 1
+
+    while left <= right:
+        mid = (left + right) // 2
+
+        # If target is found, return its index
+        if arr[mid] == target:
+            return mid
+
+        # If target is greater, ignore left half
+        elif arr[mid] < target:
+            left = mid + 1
+
+        # If target is smaller, ignore right half
+        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_basic():
+    """Test basic binary search functionality."""
+    arr = [1, 3, 5, 7, 9, 11, 13]
+    assert binary_search(arr, 7) == 3  # 7 is at index 3
+    assert binary_search(arr, 13) == 6  # Last element
+    assert binary_search(arr, 1) == 0   # First element
+
+def test_binary_search_not_found():
+    """Test when target is not in the array."""
+    arr = [1, 3, 5, 7, 9, 11, 13]
+    assert binary_search(arr, 4) == -1
+    assert binary_search(arr, 0) == -1
+    assert binary_search(arr, 14) == -1
+
+def test_binary_search_edge_cases():
+    """Test edge cases like empty list and single-element list."""
+    assert binary_search([], 5) == -1
+    assert binary_search([1], 1) == 0
+    assert binary_search([1], 2) == -1
+
+def test_binary_search_invalid_inputs():
+    """Test error handling for invalid inputs."""
+    # Not a list
+    with pytest.raises(TypeError, match="Input must be a list"):
+        binary_search("not a list", 5)
+
+    # 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_duplicate_values():
+    """Test handling of duplicate values."""
+    arr = [1, 2, 2, 3, 3, 3, 4, 5]
+    # Returns the index of the first occurrence of the target
+    assert binary_search(arr, 3) in [3, 4, 5]
+    assert binary_search(arr, 2) in [1, 2]