diff --git a/container-with-most-water/njngwn.py b/container-with-most-water/njngwn.py
new file mode 100644
index 0000000000..c488b437d0
--- /dev/null
+++ b/container-with-most-water/njngwn.py
@@ -0,0 +1,18 @@
+class Solution:
+    # Time Complexity: O(n), n: len(height)
+    # Space Complexity: O(1)
+    def maxArea(self, height: List[int]) -> int:
+        left, right = 0, len(height) - 1
+        max_area = 0
+
+        while left < right:
+            w = right - left
+            h = min(height[left], height[right])
+            max_area = max(max_area, w * h)
+
+            if height[left] <= height[right]:
+                left += 1
+            else:
+                right -= 1
+
+        return max_area
diff --git a/design-add-and-search-words-data-structure/njngwn.py b/design-add-and-search-words-data-structure/njngwn.py
new file mode 100644
index 0000000000..dc2ec3dd95
--- /dev/null
+++ b/design-add-and-search-words-data-structure/njngwn.py
@@ -0,0 +1,42 @@
+class TrieNode:
+    def __init__(self):
+        self.children = {}
+        self.isEnd = False
+
+
+class WordDictionary:
+
+    def __init__(self):
+        self.root = TrieNode()
+
+    def addWord(self, word: str) -> None:
+        node = self.root
+        for ch in word:
+            if ch not in node.children:
+                node.children[ch] = TrieNode()
+            node = node.children[ch]
+
+        node.isEnd = True
+
+    def search(self, word: str) -> bool:
+        def dfs(node: TrieNode, idx: int) -> bool:
+            if idx == len(word):
+                return node.isEnd
+
+            ch = word[idx]
+            if ch == '.':
+                for child in node.children.values():
+                    if dfs(child, idx + 1):
+                        return True
+                return False
+
+            if ch not in node.children:
+                return False
+            return dfs(node.children[ch], idx + 1)
+
+        return dfs(self.root, 0)
+
+# Your WordDictionary object will be instantiated and called as such:
+# obj = WordDictionary()
+# obj.addWord(word)
+# param_2 = obj.search(word)
diff --git a/longest-increasing-subsequence/njngwn.py b/longest-increasing-subsequence/njngwn.py
new file mode 100644
index 0000000000..3b20329fe8
--- /dev/null
+++ b/longest-increasing-subsequence/njngwn.py
@@ -0,0 +1,23 @@
+class Solution:
+    # Time Complexity: O(n*log(n)), n: len(nums)
+    # Space Complexity: O(n), n: len(nums)
+    def lengthOfLIS(self, nums: List[int]) -> int:
+        seq = []
+
+        for num in nums:
+            if not seq or (seq[-1] < num):
+                seq.append(num)
+                continue
+
+            # overwrite the smaller value with binary search
+            left, right = 0, len(seq)
+            while left < right:
+                mid = (left + right) // 2
+                if seq[mid] < num:
+                    left = mid + 1
+                else:
+                    right = mid
+
+            seq[left] = num
+
+        return len(seq)
diff --git a/spiral-matrix/njngwn.py b/spiral-matrix/njngwn.py
new file mode 100644
index 0000000000..60ac61add7
--- /dev/null
+++ b/spiral-matrix/njngwn.py
@@ -0,0 +1,30 @@
+class Solution:
+    # Time Complexity: O(n*m), n: len(matrix), m: len(matrix[0])
+    # Space Complexity: O(1)
+    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
+        result = []
+        direction = [(0, -1), (0, 1), (-1, 0), (1, 0)]  # left, right, up, down
+        left, right, top, bottom = 0, len(matrix[0])-1, 0, len(matrix)-1    # borders
+        i, j, d = 0, 0, direction[1]
+
+        while left <= right and top <= bottom:
+            # change direction and borders
+            if j == right and d == direction[1]:
+                d = direction[3] # right -> down
+                top += 1
+            elif i == bottom and d == direction[3]:
+                d = direction[0]  # down -> left
+                right -= 1
+            elif j == left and d == direction[0]:
+                d = direction[2]  # left -> up
+                bottom -= 1
+            elif i == top and d == direction[2]:
+                d = direction[1]  # up -> right
+                left += 1
+
+            # append val to the result
+            result.append(matrix[i][j])
+            i += d[0]
+            j += d[1]
+
+        return result
diff --git a/valid-parentheses/njngwn.py b/valid-parentheses/njngwn.py
new file mode 100644
index 0000000000..6553ccff47
--- /dev/null
+++ b/valid-parentheses/njngwn.py
@@ -0,0 +1,25 @@
+from collections import deque
+
+
+class Solution:
+    # Time Complexity: O(n), n: len(s)
+    # Space Complexity: O(n), n: len(s)
+    def isValid(self, s: str) -> bool:
+        if len(s) % 2 != 0:
+            return False
+
+        stack = deque()
+
+        for ch in s:
+            if ch == '(' or ch == '[' or ch == '{':
+                stack.append(ch)
+            elif len(stack) != 0:
+                top = stack.pop()
+                if (top == '(' and ch == ')') or (top == '[' and ch == ']') or (top == '{' and ch == '}'):
+                    continue
+                else:
+                    return False
+            else:
+                return False
+
+        return len(stack) == 0