valid palindrome solution

Author: JeonJe

valid-palindrome/JeonJe.java

@@ -0,0 +1,23 @@
+import java.util.*;
+
+// TC: O(n)
+// SC: O(n)
+class Solution {
+    public boolean isPalindrome(String s) {
+        StringBuilder sb = new StringBuilder();
+
+        for (char c : s.toCharArray()) {
+            if (Character.isLetterOrDigit(c)) {
+                sb.append(Character.toLowerCase(c));
+            }
+        }
+
+        for (int i = 0; i < sb.length() / 2; i++) {
+            if (sb.charAt(i) != sb.charAt(sb.length() - 1 - i)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+}