diff --git a/construct-binary-tree-from-preorder-and-inorder-traversal/hwanmini.js b/construct-binary-tree-from-preorder-and-inorder-traversal/hwanmini.js
new file mode 100644
index 000000000..de2a17a47
--- /dev/null
+++ b/construct-binary-tree-from-preorder-and-inorder-traversal/hwanmini.js
@@ -0,0 +1,14 @@
+// 시간복잡도: O(n2)
+// 공간복잡도: O(n)
+
+var buildTree = function(preorder, inorder) {
+    if (!preorder.length || !inorder.length) return null;
+
+    const root = new TreeNode(preorder[0]);
+    const mid = inorder.indexOf(root.val);
+
+    root.left = buildTree(preorder.slice(1, mid + 1), inorder.slice(0, mid));
+    root.right = buildTree(preorder.slice(mid + 1), inorder.slice(mid + 1));
+
+    return root;
+};
diff --git a/counting-bits/hwanmini.js b/counting-bits/hwanmini.js
new file mode 100644
index 000000000..92c957a99
--- /dev/null
+++ b/counting-bits/hwanmini.js
@@ -0,0 +1,21 @@
+// 시간복잡도 O(n * log n)
+// 공간복잡도 O(n)
+
+/**
+ * @param {number} n
+ * @return {number[]}
+ */
+var countBits = function(n) {
+    const result = []
+
+    for (let i = 0 ; i <= n; i++) {
+        const binaryNumber = i.toString(2)
+        const oneLength = binaryNumber.replaceAll('0','').length
+
+        result.push(oneLength)
+    }
+
+    return result
+};
+
+console.log(countBits(5))
diff --git a/valid-anagram/hwanmini.js b/valid-anagram/hwanmini.js
new file mode 100644
index 000000000..f7e2987dc
--- /dev/null
+++ b/valid-anagram/hwanmini.js
@@ -0,0 +1,28 @@
+// 시간복잡도: O(n)
+// 공간복잡도: O(k)
+
+/**
+ * @param {string} s
+ * @param {string} t
+ * @return {boolean}
+ */
+var isAnagram = function(s, t) {
+    if (s.length !== t.length) return false
+
+    const checkMap = new Map();
+
+    for (let i = 0; i < s.length; i++) {
+        checkMap.set(s[i], (checkMap.get(s[i]) || 0) + 1)
+    }
+
+
+    for (let j = 0; j < t.length; j++) {
+        if (!checkMap.get(t[j]) || checkMap.get(t[j]) < 0) return false
+        checkMap.set(t[j], (checkMap.get(t[j]) || 0 ) - 1);
+    }
+
+    return true
+};
+
+
+console.log(isAnagram("anagram","nagaram"))