Create sliding_window.py

greedy_methods/sliding_window.py

@@ -0,0 +1,64 @@
+def sliding_window(input_string: str) -> int:
+    """
+    This function takes a string and returns the length of the longest substring
+    without repeating characters using the sliding window algorithm.
+
+    It runs in O(n) time, where n is the length of the string. The sliding window
+    approach ensures that each character is processed at most twice.
+
+    Args:
+        input_string: A string input.
+
+    Returns:
+        int: Length of the longest substring without repeating characters.
+
+    Raises:
+        TypeError: If the input is not a string.
+
+    Examples:
+    >>> sliding_window("abcabcbb")
+    3
+    >>> sliding_window("bbbbb")
+    1
+    >>> sliding_window("pwwkew")
+    3
+    >>> sliding_window("")
+    0
+    >>> sliding_window("abcdefg")
+    7
+    >>> sliding_window("abccba")
+    3
+    >>> sliding_window("a"*10000)
+    1
+    """
+    # Error handling for non-string inputs
+    if not isinstance(input_string, str):
+        raise TypeError("Input must be a string")
+
+    # Handle empty string case immediately
+    if len(input_string) == 0:
+        return 0
+
+    # Dictionary to store the most recent index of each character
+    char_index_map: dict[str, int] = {}
+
+    # Initialize the sliding window pointers
+    left: int = 0
+    max_len: int = 0
+    # Traverse the string with a right pointer
+    for right, char in enumerate(input_string):
+        if char in char_index_map and char_index_map[char] >= left:
+            # Move the left pointer to avoid repeating characters
+            left = char_index_map[char] + 1
+        # Update the latest index of the character
+        char_index_map[char] = right
+        # Calculate the current length of the window
+        current_len = right - left + 1
+        max_len = max(max_len, current_len)
+    return max_len
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()