diff --git a/combination-sum/mrlee7.py b/combination-sum/mrlee7.py
new file mode 100644
index 0000000000..6f1c3da829
--- /dev/null
+++ b/combination-sum/mrlee7.py
@@ -0,0 +1,20 @@
+from typing import List
+
+
+class Solution:
+    def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]:
+        result, nums = list(), list()
+
+        def dfs(start_position, total_sum):
+            if total_sum > target:
+                return
+            if total_sum == target:
+                result.append(nums[:])
+            for idx in range(start_position, len(candidates)):
+                num = candidates[idx]
+                nums.append(num)
+                dfs(idx, total_sum + num)
+                nums.pop()
+
+        dfs(0, 0)
+        return result
diff --git a/number-of-1-bits/mrlee7.py b/number-of-1-bits/mrlee7.py
new file mode 100644
index 0000000000..6b1b7f37d8
--- /dev/null
+++ b/number-of-1-bits/mrlee7.py
@@ -0,0 +1,8 @@
+class Solution:
+    def hammingWeight(self, n: int) -> int:
+        result = 0
+
+        while n > 0:
+            result += n % 2
+            n //= 2
+        return result
diff --git a/valid-palindrome/mrlee7.py b/valid-palindrome/mrlee7.py
new file mode 100644
index 0000000000..e4983e01d3
--- /dev/null
+++ b/valid-palindrome/mrlee7.py
@@ -0,0 +1,7 @@
+import re
+
+
+class Solution:
+    def isPalindrome(self, s: str) -> bool:
+        result = re.sub(r'[^a-zA-Z0-9]', '', s).lower()
+        return result == result[::-1]