diff --git a/longest-consecutive-sequence/hwanmini.js b/longest-consecutive-sequence/hwanmini.js
new file mode 100644
index 000000000..880d7b2ae
--- /dev/null
+++ b/longest-consecutive-sequence/hwanmini.js
@@ -0,0 +1,29 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var longestConsecutive = function(nums) {
+    if (nums.length === 0) return 0;
+
+    const numSet = new Set(nums);
+    let maxSequenceLength = 0;
+
+    for (const num of numSet) {
+        if (!numSet.has(num - 1)) {
+            let currentNum = num;
+            let currentLength = 1;
+
+            while (numSet.has(currentNum + 1)) {
+                currentNum++;
+                currentLength++;
+            }
+
+            maxSequenceLength = Math.max(maxSequenceLength, currentLength);
+        }
+    }
+
+    return maxSequenceLength;
+};
+
+console.log(longestConsecutive([100, 4, 200, 1, 3, 2]));
+console.log(longestConsecutive([0, 3, 7, 2, 5, 8, 4, 6, 0, 1]));
diff --git a/missing-number/hwanmini.js b/missing-number/hwanmini.js
new file mode 100644
index 000000000..23bdef4b6
--- /dev/null
+++ b/missing-number/hwanmini.js
@@ -0,0 +1,19 @@
+// 시간복잡도 O(n log n)
+// 공간복잡도 O(n)
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var missingNumber = function(nums) {
+    nums.sort((a,b) => a - b);
+
+    for (let i = 0 ; i <= nums.length; i++) {
+        if (i !== nums[i]) return i
+    }
+
+};
+
+console.log(missingNumber([3, 0, 1]))
+console.log(missingNumber([0, 1]))
+console.log(missingNumber([9,6,4,2,3,5,7,0,1]))
diff --git a/valid-palindrome/hwanmini.js b/valid-palindrome/hwanmini.js
new file mode 100644
index 000000000..cad935a9a
--- /dev/null
+++ b/valid-palindrome/hwanmini.js
@@ -0,0 +1,29 @@
+// 시간복잡도: O(n)
+// 공간복잡도: O(n)
+
+/**
+ * @param {string} s
+ * @return {boolean}
+ */
+var isPalindrome = function(s) {
+    const strs = s.replace(/[^a-z0-9]/gi, '').toLowerCase();
+
+    let leftIdx = 0;
+    let rightIdx = strs.length - 1
+
+    while (leftIdx <= rightIdx) {
+        if (strs[leftIdx] !== strs[rightIdx]) return false
+
+        leftIdx++
+        rightIdx--
+    }
+
+
+    return true
+};
+
+const s = "A man, a plan, a canal: Panama"
+
+
+console.log(isPalindrome(s))
+
diff --git a/word-search/hwanmini.js b/word-search/hwanmini.js
new file mode 100644
index 000000000..8944bc1aa
--- /dev/null
+++ b/word-search/hwanmini.js
@@ -0,0 +1,69 @@
+
+// m은 board의 행 수, n은 board의 열 수, 4(상하좌우), l(word)
+
+// 시간복잡도: O(m * n * 4L)
+// 공간복잡도: O(m * n)
+
+const d_row = [1, -1, 0, 0]
+const d_col = [0, 0, -1, 1]
+
+
+const isMoveBoard = (new_row, new_col, board) => {
+    return new_row >= 0 && new_row < board.length && new_col >= 0 && new_col < board[0].length
+}
+
+
+/**
+ * @param {character[][]} board
+ * @param {string} word
+ * @return {boolean}
+ */
+var exist = function(board, word) {
+    let result = false
+
+    const visited = Array.from({length: board.length} , () => Array.from({length: board[0].length}).fill(false))
+
+    const dfs = (strs, row, col, count) => {
+
+        if (strs[count] !== word[count]) return
+        if (strs.length > word.length) return
+
+        if (strs === word)  {
+            result = true
+            return
+        }
+
+        for (let i = 0 ; i < d_row.length; i++) {
+            const new_row = row + d_row[i]
+            const new_col = col + d_col[i]
+
+            if (isMoveBoard(new_row, new_col, board) && visited[new_row][new_col] !== true){
+                visited[new_row][new_col] = true
+                dfs(strs+board[new_row][new_col], new_row, new_col, count+1)
+                visited[new_row][new_col] = false
+            }
+        }
+
+
+
+    }
+
+
+    for (let row = 0 ; row < board.length ; row++) {
+        for (let col = 0 ; col < board[0].length ; col++) {
+            visited[row][col] = true
+            dfs(board[row][col], row, col , 0)
+            visited[row][col] = false
+        }
+    }
+
+
+    return result
+};
+
+console.log(exist([["A","B","C","E"],
+    ["S","F","C","S"],
+    ["A","D","E","E"]], "ABCCED"))
+console.log(exist([["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], "SEE"))
+console.log(exist([["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], "ABCB"))
+