diff --git a/container-with-most-water/sejineer.py b/container-with-most-water/sejineer.py
new file mode 100644
index 000000000..37db7314b
--- /dev/null
+++ b/container-with-most-water/sejineer.py
@@ -0,0 +1,17 @@
+"""
+시간 복잡도: O(N)
+공간 복잡도: O(1)
+"""
+class Solution:
+    def maxArea(self, height: List[int]) -> int:
+        result = 0
+        start, end = 0, len(height) - 1
+
+        while start < end:
+            area = (end - start) * min(height[start], height[end])
+            result = max(result, area)
+            if height[start] < height[end]:
+                start += 1
+            else:
+                end -= 1
+        return result
diff --git a/design-add-and-search-words-data-structure/sejineer.py b/design-add-and-search-words-data-structure/sejineer.py
new file mode 100644
index 000000000..0211a8afd
--- /dev/null
+++ b/design-add-and-search-words-data-structure/sejineer.py
@@ -0,0 +1,26 @@
+class WordDictionary:
+
+    def __init__(self):
+        self.root = {"$": True}
+        
+
+    def addWord(self, word: str) -> None:
+        node = self.root
+        for ch in word:
+            if ch not in node:
+                node[ch] = {"$": False}
+            node = node[ch]
+        node["$"] = True
+
+    def search(self, word: str) -> bool:
+        def dfs(node, idx):
+            if idx == len(word):
+                return node["$"]
+            ch = word[idx]
+            if ch in node:
+                return dfs(node[ch], idx + 1)
+            elif ch == ".":
+                return any(dfs(node[k], idx + 1) for k in node if k != "$")
+            else:
+                return False
+        return dfs(self.root, 0)
diff --git a/longest-increasing-subsequence/sejineer.py b/longest-increasing-subsequence/sejineer.py
new file mode 100644
index 000000000..986d26905
--- /dev/null
+++ b/longest-increasing-subsequence/sejineer.py
@@ -0,0 +1,16 @@
+"""
+시간 복잡도: O(Nlog(N))
+공간 복잡도: O(N)
+"""
+from bisect import bisect_left
+
+class Solution:
+    def lengthOfLIS(self, nums: List[int]) -> int:
+        sub = []
+        for num in nums:
+            index = bisect_left(sub, num)
+            if index == len(sub):
+                sub.append(num)
+            else:
+                sub[index] = num
+        return len(sub)
diff --git a/spiral-matrix/sejineer.py b/spiral-matrix/sejineer.py
new file mode 100644
index 000000000..ef16c95d4
--- /dev/null
+++ b/spiral-matrix/sejineer.py
@@ -0,0 +1,29 @@
+"""
+시간 복잡도: O(n * m)
+공간 복잡도: O(n * m)
+"""
+class Solution:
+    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
+        n, m = len(matrix), len(matrix[0])
+        dx = [1, 0, -1, 0]
+        dy = [0, 1, 0, -1]
+        state = 0
+        vis = [[False] * m for _ in range(n)]
+
+        result = [matrix[0][0]]
+        vis[0][0] = True
+        x, y = 0, 0
+        
+        while len(result) < n * m:
+            nx = x + dx[state % 4]
+            ny = y + dy[state % 4]
+
+            if not (0 <= nx < m) or not (0 <= ny < n) or vis[ny][nx]:
+                state += 1
+                continue
+            
+            vis[ny][nx] = True
+            result.append(matrix[ny][nx])
+            x, y = nx, ny
+        
+        return result
diff --git a/valid-parentheses/sejineer.py b/valid-parentheses/sejineer.py
new file mode 100644
index 000000000..317a28953
--- /dev/null
+++ b/valid-parentheses/sejineer.py
@@ -0,0 +1,21 @@
+"""
+시간 복잡도: O(N)
+공간 복잡도: O(N)
+"""
+class Solution:
+    def isValid(self, s: str) -> bool:
+        pair = {'(': ')', '{': '}', '[': ']'}
+        stack = []
+        for c in s:
+            if c in ('(', '{', '['):
+                stack.append(c)
+            else:
+                if stack:
+                    cur = stack.pop()
+                    if pair[cur] == c:
+                        continue
+                    else:
+                        return False
+                else:
+                    return False
+        return not stack