encode and decode strings solution

Author: jylee2033

encode-and-decode-strings/jylee2033.py

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+class Solution:
+    """
+    @param: strs: a list of strings
+    @return: encodes a list of strings to a single string.
+    """
+    def encode(self, strs):
+        # write your code here
+        # Encode each word with its length prefix and a "#"
+        # ["C#", "&"] -> "2#C#1#&"
+        encoded_str = ""
+        
+        for word in strs:
+            encoded_str += f"{len(word)}#{word}"
+
+        return encoded_str
+        
+    """
+    @param: str: A string
+    @return: decodes a single string to a list of strings
+    """
+    def decode(self, str):
+        # write your code here
+        # "2#C#1#&" -> ["C#", "&"]
+        decoded_lst = []
+        char_count = 0
+        reading_word = False
+        word = ""
+        length_str = ""
+
+        if str == "":
+            return [""]
+
+        for ch in str:
+            if ch == "#" and not reading_word:
+                # Finished reading the length prefix
+                # Switch to word-reading mode
+                char_count = int(length_str)
+                length_str = ""
+                reading_word = True
+
+            elif not reading_word:
+                # Accumulate digits for the length prefix
+                length_str += ch
+
+            else:
+                # reading_word is True
+                word += ch
+                char_count -= 1
+
+                if char_count == 0:
+                    reading_word = False
+                    decoded_lst.append(word)
+                    word = ""
+
+        return decoded_lst
+
+# Time Complexity: O(N)
+# Space Complexity: O(N)