Enhance split function with separator validation

strings/split.py

@@ -1,33 +1,36 @@
 def split(string: str, separator: str = " ") -> list:
     """
-    Will split the string up into all the values separated by the separator
-    (defaults to spaces)
-
+    Will split the string up into all the values separated by the separator (defaults to spaces)
     >>> split("apple#banana#cherry#orange",separator='#')
     ['apple', 'banana', 'cherry', 'orange']
-
     >>> split("Hello there")
     ['Hello', 'there']
-
     >>> split("11/22/63",separator = '/')
     ['11', '22', '63']
-
     >>> split("12:43:39",separator = ":")
     ['12', '43', '39']
-
     >>> split(";abbb;;c;", separator=';')
     ['', 'abbb', '', 'c', '']
     """
+    if len(separator) != 1:
+        raise ValueError("separator must be exactly one character long")
 
-    split_words = []
+    # If the input string is empty, Python's split returns ['']
+    if not string:
+        return [""]
 
+    split_words = []
     last_index = 0
+
+    # Single-pass scan using string slicing for optimal memory and speed
     for index, char in enumerate(string):
         if char == separator:
             split_words.append(string[last_index:index])
             last_index = index + 1
-        if index + 1 == len(string):
-            split_words.append(string[last_index : index + 1])
+
+    # Append the remaining trailing substring after the last separator
+    split_words.append(string[last_index:])
+
     return split_words