adding updates

src/my_project/interviews/google_top_exercises/round_1/15_encode_and_decode_strings.py

@@ -0,0 +1,30 @@
+from typing import List
+
+
+
+class Codec:
+    def encode(self, strs: List[str]) -> str:
+        """Encodes a list of strings to a single string.
+
+        Length-prefix each string as "<len>#<string>". The delimiter '#'
+        is unambiguous because we always know the exact number of chars
+        to read from the length that precedes it, so any character
+        (including '#') may appear inside a string.
+        """
+        return "".join(f"{len(s)}#{s}" for s in strs)
+
+    def decode(self, s: str) -> List[str]:
+        """Decodes a single string to a list of strings.
+        """
+        strs = []
+        i = 0
+        n = len(s)
+        while i < n:
+            # Read the length up to the '#' delimiter.
+            j = s.index("#", i)
+            length = int(s[i:j])
+            # The string is the next `length` chars after the '#'.
+            start = j + 1
+            strs.append(s[start:start + length])
+            i = start + length
+        return strs