valid palindrome solution

Author: eunhwa99

valid-palindrome/eunhwa99.java

@@ -0,0 +1,23 @@
+class Solution {
+    public boolean isPalindrome(String s) {
+        StringBuilder str = new StringBuilder();
+    
+        for (int i = 0; i < s.length(); i++) {
+            char c = s.charAt(i);
+            if (Character.isLetterOrDigit(c)) {
+                str.append(Character.toLowerCase(c));  
+            }
+        }
+        
+        int left = 0, right = str.length() - 1;
+        while (left < right) {
+            if (str.charAt(left) != str.charAt(right)) {
+                return false;  
+            }
+            left++;
+            right--;
+        }
+        
+        return true;  
+    }
+}