[hoonjichoi1] WEEK 03 solutions

valid-palindrome/hoonjichoi1.java

@@ -0,0 +1,23 @@
+class Solution {
+    public boolean isPalindrome(String s) {
+
+        // removing all non-alphanumeric characters and convert them to lower case
+        String conveted = s.replaceAll("[^a-zA-Z0-9]", "").toLowerCase();
+
+        // early return of the empty string case
+        if (conveted.length() == 0) {
+            return true;
+        }
+
+        // check the symmetry
+        int left = 0, right = conveted.length() - 1;
+        while (left <= right) {
+            if (conveted.charAt(left) != conveted.charAt(right)) {
+                return false;
+            }
+            left++;
+            right--;
+        }
+        return true;
+    }
+}