diff --git a/best-time-to-buy-and-sell-stock/reeseo3o.js b/best-time-to-buy-and-sell-stock/reeseo3o.js
new file mode 100644
index 000000000..637a660b8
--- /dev/null
+++ b/best-time-to-buy-and-sell-stock/reeseo3o.js
@@ -0,0 +1,31 @@
+// Step 1. 브루트 포스
+// 시간 복잡도: O(n²)
+const maxProfitBrute = (prices) => {
+    let maxProfit = 0;
+
+    for (let i = 0; i < prices.length; i++) {
+        for (let j = i + 1; j < prices.length; j++) {
+            const profit = prices[j] - prices[i];
+            maxProfit = Math.max(maxProfit, profit);
+        }
+    }
+
+    return maxProfit;
+}
+
+// Step 2. 최적 풀이
+// 시간 복잡도: O(n)
+const maxProfit = (prices) => {
+    let minPrice = Infinity;
+    let maxProfit = 0;
+
+    for (const price of prices) {
+        if (price < minPrice) {
+            minPrice = price;
+        } else {
+            maxProfit = Math.max(maxProfit, price - minPrice);
+        }
+    }
+
+    return maxProfit;
+}
diff --git a/group-anagrams/reeseo3o.js b/group-anagrams/reeseo3o.js
new file mode 100644
index 000000000..f66648033
--- /dev/null
+++ b/group-anagrams/reeseo3o.js
@@ -0,0 +1,19 @@
+/**
+ * TC: O(n * k log k) — 각 단어(k) 정렬 × n개
+ * SC: O(n * k)
+ */
+const groupAnagrams = (strs) => {
+    const map = new Map();
+
+    for (const str of strs) {
+        const key = str.split("").sort().join("");
+
+        if (!map.has(key)) {
+            map.set(key, []);
+        }
+
+        map.get(key).push(str);
+    }
+
+    return Array.from(map.values());
+};