diff --git a/binary-tree-level-order-traversal/printjin-gmailcom.py b/binary-tree-level-order-traversal/printjin-gmailcom.py
new file mode 100644
index 000000000..0b16125a6
--- /dev/null
+++ b/binary-tree-level-order-traversal/printjin-gmailcom.py
@@ -0,0 +1,13 @@
+class Solution:
+    def levelOrder(self, root):
+        result = []
+        def dfs(node, level):
+            if not node:
+                return
+            if len(result) == level:
+                result.append([])
+            result[level].append(node.val)
+            dfs(node.left, level + 1)
+            dfs(node.right, level + 1)
+        dfs(root, 0)
+        return result
diff --git a/counting-bits/printjin-gmailcom.py b/counting-bits/printjin-gmailcom.py
new file mode 100644
index 000000000..c34a736df
--- /dev/null
+++ b/counting-bits/printjin-gmailcom.py
@@ -0,0 +1,6 @@
+class Solution:
+    def countBits(self, n):
+        ans = [0] * (n + 1)
+        for i in range(1, n + 1):
+            ans[i] = ans[i >> 1] + (i & 1)
+        return ans
diff --git a/house-robber-ii/printjin-gmailcom.py b/house-robber-ii/printjin-gmailcom.py
new file mode 100644
index 000000000..c9d617870
--- /dev/null
+++ b/house-robber-ii/printjin-gmailcom.py
@@ -0,0 +1,10 @@
+class Solution:
+    def rob(self, nums):
+        if len(nums) == 1:
+            return nums[0]
+        def rob_linear(houses):
+            prev = curr = 0
+            for num in houses:
+                prev, curr = curr, max(curr, prev + num)
+            return curr
+        return max(rob_linear(nums[:-1]), rob_linear(nums[1:]))
diff --git a/meeting-rooms-ii/printjin-gmailcom.py b/meeting-rooms-ii/printjin-gmailcom.py
new file mode 100644
index 000000000..32b43070f
--- /dev/null
+++ b/meeting-rooms-ii/printjin-gmailcom.py
@@ -0,0 +1,14 @@
+class Solution:
+    def minMeetingRooms(self, intervals):
+        if not intervals:
+            return 0
+        starts = sorted(i[0] for i in intervals)
+        ends = sorted(i[1] for i in intervals)
+        s = e = rooms = 0
+        while s < len(intervals):
+            if starts[s] < ends[e]:
+                rooms += 1
+            else:
+                e += 1
+            s += 1
+        return rooms
diff --git a/word-search-ii/printjin-gmailcom.py b/word-search-ii/printjin-gmailcom.py
new file mode 100644
index 000000000..0af33e32f
--- /dev/null
+++ b/word-search-ii/printjin-gmailcom.py
@@ -0,0 +1,30 @@
+class Solution:
+    def findWords(self, board: List[List[str]], words: List[str]) -> List[str]:
+        trie = {}
+        for word in words:
+            node = trie
+            for char in word:
+                node = node.setdefault(char, {})
+            node["$"] = word
+        rows, cols = len(board), len(board[0])
+        result = []
+        def dfs(r, c, node):
+            char = board[r][c]
+            if char not in node:
+                return
+            next_node = node[char]
+            word = next_node.pop("$", None)
+            if word:
+                result.append(word)
+            board[r][c] = "#"
+            for dr, dc in [(-1,0),(1,0),(0,-1),(0,1)]:
+                nr, nc = r + dr, c + dc
+                if 0 <= nr < rows and 0 <= nc < cols and board[nr][nc] != "#":
+                    dfs(nr, nc, next_node)
+            board[r][c] = char
+            if not next_node:
+                node.pop(char)
+        for r in range(rows):
+            for c in range(cols):
+                dfs(r, c, trie)
+        return result