diff --git a/disappeared_no.py b/disappeared_no.py
new file mode 100644
index 00000000..64ff1a79
--- /dev/null
+++ b/disappeared_no.py
@@ -0,0 +1,18 @@
+class Solution:
+    def findDisappearedNumbers(self, nums):
+        n = len(nums)
+
+        for i in range(n):
+            idx = abs(nums[i]) - 1
+            if nums[idx] > 0:
+                nums[idx] *= -1
+
+        result = []
+        for i in range(n):
+            if nums[i] > 0:
+                result.append(i + 1)
+
+        return result
+
+# Time: O(n)
+# Space: O(h)
\ No newline at end of file
diff --git a/game_of_life.py b/game_of_life.py
new file mode 100644
index 00000000..f93632db
--- /dev/null
+++ b/game_of_life.py
@@ -0,0 +1,30 @@
+class Solution:
+    def gameOfLife(self, board):
+        dirs = [(-1,-1), (-1,0), (-1,1), (0,-1), (0,1), (1,-1), (1,0), (1,1)]
+        m, n = len(board), len(board[0])
+
+        def getCount(i, j):
+            count = 0
+            for dx, dy in dirs:
+                r, c = i + dx, j + dy
+                if 0 <= r < m and 0 <= c < n:
+                    if board[r][c] == 1 or board[r][c] == 2:
+                        count += 1
+            return count
+
+        for i in range(m):
+            for j in range(n):
+                cnt = getCount(i, j)
+                if board[i][j] == 0 and cnt == 3:
+                    board[i][j] = 3
+                elif board[i][j] == 1 and (cnt < 2 or cnt > 3):
+                    board[i][j] = 2
+
+        for i in range(m):
+            for j in range(n):
+                if board[i][j] == 2:
+                    board[i][j] = 0
+                elif board[i][j] == 3:
+                    board[i][j] = 1
+# Time: O(m + n)
+# Space: O(1)
\ No newline at end of file