Merge pull request #2112 from WHYjun/week3

[WHYjun] WEEK 03 solutions=

Author: TonyKim9401

number-of-1-bits/WHYjun.py

@@ -0,0 +1,7 @@
+class Solution:
+    def hammingWeight(self, n: int) -> int:
+        result = 0
+        for i in range(32):
+            if (n >> i) & 1:
+                result += 1
+        return result

valid-palindrome/WHYjun.py

@@ -0,0 +1,14 @@
+class Solution:
+    def isPalindrome(self, s: str) -> bool:
+        s = [c.lower() for c in s if c.isalnum()]
+
+        if len(s) == 1:
+            return True
+        
+        l, r = 0, len(s) - 1
+        while l < r:
+            if s[l] != s[r]:
+                return False
+            l += 1
+            r -= 1
+        return True