Added top-k and endcode-decode solutions

Author: nhistory

encode-and-decode-strings/nhistory.js

@@ -0,0 +1,43 @@
+class Solution {
+  /**
+   * @param {string[]} strs
+   * @returns {string}
+   */
+  encode(strs) {
+    let result = "";
+    for (let str of strs) {
+      result += str.length.toString() + "#" + str;
+    }
+    return result;
+  }
+
+  /**
+   * @param {string} str
+   * @returns {string[]}
+   */
+  decode(str) {
+    let result = [];
+    let i = 0;
+
+    while (i < str.length) {
+      // Find the position of the next '#'
+      let j = i;
+      while (str[j] !== "#") {
+        j++;
+      }
+
+      // Length of the next string
+      const len = parseInt(str.slice(i, j));
+      i = j + 1; // Move past the '#'
+
+      // Extract the string of length 'len'
+      result.push(str.slice(i, i + len));
+      i += len; // Move past the extracted string
+    }
+
+    return result;
+  }
+}
+
+// TC: O(n),O(n)
+// SC: O(n),O(n)

top-k-frequent-elements/nhistory.js

@@ -0,0 +1,14 @@
+var topKFrequent = function (nums, k) {
+  // 1. Hashmap { num : frequency }
+  let map = {};
+
+  // 2. Iterate counts frequency of each value
+  for (num of nums) {
+    // Check there is already num key or not
+    if (!map[num]) map[num] = 0;
+    map[num]++;
+  }
+
+  // 3. Sort frequency and return sliced array
+  return [...Object.keys(map)].sort((a, b) => map[b] - map[a]).slice(0, k);
+};