Implement Custom String Reversal Function Using Two-Pointer Approach

src/string_reversal.py

@@ -0,0 +1,30 @@
+def reverse_string(input_str):
+    """
+    Reverse a given string manually, without using slice notation or reverse().
+
+    Args:
+        input_str (str): The input 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_str, str):
+        raise TypeError("Input must be a string")
+
+    # Convert string to list of characters for easier manipulation
+    chars = list(input_str)
+
+    # Manually reverse the list of characters
+    left, right = 0, len(chars) - 1
+    while left < right:
+        # Swap characters from both ends
+        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_basic_string_reversal():
+    """Test basic string reversal"""
+    assert reverse_string("hello") == "olleh"
+    assert reverse_string("python") == "nohtyp"
+
+def test_empty_string():
+    """Test reversal of an empty string"""
+    assert reverse_string("") == ""
+
+def test_single_character():
+    """Test reversal of a single character"""
+    assert reverse_string("a") == "a"
+
+def test_string_with_spaces():
+    """Test reversal of string with spaces"""
+    assert reverse_string("hello world") == "dlrow olleh"
+
+def test_string_with_special_characters():
+    """Test reversal of string with special characters"""
+    assert reverse_string("!@#$%") == "%$#@!"
+
+def test_unicode_string():
+    """Test reversal of unicode string"""
+    assert reverse_string("こんにちは") == "はちにんこ"
+
+def test_invalid_input_type():
+    """Test that TypeError is raised for non-string inputs"""
+    with pytest.raises(TypeError, match="Input must be a string"):
+        reverse_string(12345)
+
+    with pytest.raises(TypeError, match="Input must be a string"):
+        reverse_string(None)