solve: encode and decode strings

Author: sounmind

encode-and-decode-strings/evan.js

@@ -0,0 +1,58 @@
+const DELIMITER = "#";
+
+/**
+ *
+ * @param {string[]} strs
+ * @returns {string}
+ */
+function encode(strs) {
+  return strs.map((s) => `${s.length}${DELIMITER}${s}`).join("");
+}
+
+/**
+ *
+ * @param {string} encodedStr
+ * @returns {string[]}
+ */
+function decode(encodedStr) {
+  const decodedStrings = [];
+  let currentIndex = 0;
+
+  while (currentIndex < encodedStr.length) {
+    let delimiterIndex = currentIndex;
+
+    while (encodedStr[delimiterIndex] !== DELIMITER) {
+      delimiterIndex += 1;
+    }
+
+    const strLength = parseInt(
+      encodedStr.substring(currentIndex, delimiterIndex)
+    );
+
+    decodedStrings.push(
+      encodedStr.substring(delimiterIndex + 1, delimiterIndex + 1 + strLength)
+    );
+
+    currentIndex = delimiterIndex + 1 + strLength;
+  }
+
+  return decodedStrings;
+}
+/**
+ * Time Complexity: O(n) where n is the length of the encoded string.
+ * Reason:
+ *  The inner operations (finding # and extracting substrings) are proportional to the size of the encoded segments
+ *  but are ultimately bounded by the total length of the input string.
+ *
+ * Space Complexity: O(k) where k is the total length of the decoded strings.
+ */
+
+/**
+ * Test cases
+ */
+const strs4 = ["longestword", "short", "mid", "tiny"];
+const encoded4 = encode(strs4);
+console.log(encoded4); // Output: "11#longestword5#short3#mid4#tiny"
+
+const decoded4 = decode(encoded4);
+console.log(decoded4); // Output: ["longestword", "short", "mid", "tiny"]