[sm9171] Week 03 solutions

number-of-1-bits/sm9171.java

@@ -0,0 +1,8 @@
+public static int hammingWeight(int n) {
+    int sum = 0;
+    while (n > 0) {
+        sum += n % 2;
+        n /= 2;
+    }
+    return sum;
+}

valid-palindrome/sm9171.java

@@ -0,0 +1,12 @@
+class Solution {
+    public boolean isPalindrome(String s) {
+        String str = s.toLowerCase().replaceAll("[^a-z0-9]","");
+        char[] charArray = str.toCharArray();
+        for (int i = 0; i < charArray.length / 2; i++) {
+            if (charArray[i] != charArray[charArray.length - i - 1]) {
+                return false;
+            }
+        }
+        return true;
+    }
+}