add solution of valid-palindrome

Author: jinhyungrhee

valid-palindrome/jinhyungrhee.java

@@ -0,0 +1,26 @@
+class Solution {
+    public boolean isPalindrome(String s) {
+
+        int len = s.length();
+
+        String target = "";
+        for (int i = 0; i < len; i++) {
+            if (Character.isLetterOrDigit(s.charAt(i))) {
+                target += Character.toLowerCase(s.charAt(i));
+            }
+        }
+
+        String reversedTarget = "";
+        for (int i = len - 1; i >= 0; i--) {
+            if (Character.isLetterOrDigit(s.charAt(i))) {
+                reversedTarget += Character.toLowerCase(s.charAt(i));
+            }
+        }
+
+        if (target.length() == 0) return true;
+        for (int i = 0; i < target.length(); i++) {
+            if (target.charAt(i) != reversedTarget.charAt(i)) return false;
+        }
+        return true;
+    }
+}