add: encode decode string

data_structures/neetcode_150/src/EncodeDecodeString.java

@@ -0,0 +1,44 @@
+package neetcode_150.src;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * Design an algorithm to encode a list of strings to a string.
+ * The encoded string is then sent over the network and is decoded back to the
+ * original list of strings.
+ */
+public class EncodeDecodeString {
+    public static void main(String[] args) {
+        List<String> original = Arrays.asList("hello", "world", "java", "encoding");
+
+        String encoded = encode(original);
+        System.out.println("Encoded: " + encoded);
+
+        List<String> decoded = decode(encoded);
+        System.out.println("Decoded: " + decoded);
+    }
+
+    public static String encode(List<String> strs) {
+        if (strs.size() == 0) {
+            return Character.toString((char) 258);
+        }
+        String separate = Character.toString((char) 257);
+        StringBuilder sb = new StringBuilder();
+        for (String s : strs) {
+            sb.append(s);
+            sb.append(separate);
+        }
+        sb.deleteCharAt(sb.length() - 1);
+        return sb.toString();
+    }
+
+    public static List<String> decode(String s) {
+        if (s.equals(Character.toString((char) 258))) {
+            return new ArrayList<>();
+        }
+        String separate = Character.toString((char) 257);
+        return Arrays.asList(s.split(separate, -1));
+    }
+}