diff --git a/best-time-to-buy-and-sell-stock/hyejjun.js b/best-time-to-buy-and-sell-stock/hyejjun.js
new file mode 100644
index 000000000..048b453d0
--- /dev/null
+++ b/best-time-to-buy-and-sell-stock/hyejjun.js
@@ -0,0 +1,27 @@
+/**
+ * @param {number[]} prices
+ * @return {number}
+ */
+var maxProfit = function (prices) {
+  let minPrice = Infinity;
+  let maxProfit = 0;
+
+  for (let i = 0; i < prices.length; i++) {
+    if (prices[i] < minPrice) {
+      minPrice = prices[i];
+    } else {
+      maxProfit = Math.max(maxProfit, prices[i] - minPrice);
+    }
+  }
+
+  return maxProfit;
+
+};
+
+console.log(maxProfit([7, 1, 5, 3, 6, 4]));
+console.log(maxProfit([7, 6, 4, 3, 1]));
+
+/*
+시간 복잡도: O(n)
+공간 복잡도: O(1)
+*/
diff --git a/group-anagrams/hyejjun.js b/group-anagrams/hyejjun.js
new file mode 100644
index 000000000..8d9f11a97
--- /dev/null
+++ b/group-anagrams/hyejjun.js
@@ -0,0 +1,32 @@
+/**
+ * @param {string[]} strs
+ * @return {string[][]}
+ */
+var groupAnagrams = function (strs) {
+  let map = new Map();
+
+  for (let str of strs) {
+    let sortedStr = str.split('').sort().join('');
+
+    if (map.has(sortedStr)) {
+      map.get(sortedStr).push(str);
+    } else {
+      map.set(sortedStr, [str]);
+    }
+  }
+
+  return Array.from(map.values());
+};
+
+console.log(groupAnagrams(["eat", "tea", "tan", "ate", "nat", "bat"]));
+console.log(groupAnagrams([""]));
+console.log(groupAnagrams(["a"]));
+
+
+/*
+시간 복잡도: O(n*k log k)
+공간 복잡도: O(n*k)
+
+n: 문자열의 개수
+k: 문자열의 최대 길이
+*/