Implement Robust String Reversal Function with Two-Pointer Approach

src/string_reversal.py

@@ -0,0 +1,33 @@
+def reverse_string(input_string):
+    """
+    Reverse a given string using manual character iteration.
+
+    Args:
+        input_string (str): The string to be reversed.
+
+    Returns:
+        str: The reversed string.
+
+    Raises:
+        TypeError: If the input is not a string.
+    """
+    # Validate input is a string
+    if not isinstance(input_string, str):
+        raise TypeError("Input must be a string")
+
+    # Handle empty string case
+    if len(input_string) <= 1:
+        return input_string
+
+    # Convert string to list for manipulation
+    chars = list(input_string)
+
+    # Swap characters from start to end
+    left, right = 0, len(chars) - 1
+    while left < right:
+        chars[left], chars[right] = chars[right], chars[left]
+        left += 1
+        right -= 1
+
+    # Convert back to string and return
+    return ''.join(chars)

tests/test_string_reversal.py

@@ -0,0 +1,35 @@
+import pytest
+from src.string_reversal import reverse_string
+
+def test_reverse_string_basic():
+    """Test basic string reversal."""
+    assert reverse_string("hello") == "olleh"
+    assert reverse_string("python") == "nohtyp"
+
+def test_reverse_string_empty():
+    """Test reversing an empty string."""
+    assert reverse_string("") == ""
+
+def test_reverse_string_with_spaces():
+    """Test reversing string with spaces."""
+    assert reverse_string("hello world") == "dlrow olleh"
+
+def test_reverse_string_special_chars():
+    """Test reversing string with special characters."""
+    assert reverse_string("a1b2c3!@#") == "#@!3c2b1a"
+
+def test_reverse_string_single_char():
+    """Test reversing a single character string."""
+    assert reverse_string("a") == "a"
+
+def test_reverse_string_mixed_characters():
+    """Test reversing string with mixed character types."""
+    assert reverse_string("Hello, World! 123") == "321 !dlroW ,olleH"
+
+def test_reverse_string_invalid_input():
+    """Test that TypeError is raised for non-string inputs."""
+    with pytest.raises(TypeError, match="Input must be a string"):
+        reverse_string(123)
+
+    with pytest.raises(TypeError, match="Input must be a string"):
+        reverse_string(None)