add solution: Valid Palindrome DaleStudy#220

Author: donghyeon95

valid-palindrome/donghyeon95.java

@@ -0,0 +1,16 @@
+/* 첫 시도
+	leetCode 기준 18ms
+ */
+
+class Solution {
+	public boolean isPalindrome(String s) {
+		// 1. remove non-alphanumeric using regex
+		String alphanumeric = s.replaceAll("[^a-zA-Z0-9]", "");
+
+		// 2. change lowerCase
+		String lowerCase = alphanumeric.toLowerCase();
+
+		// 3. compare reverse String
+		return lowerCase.contentEquals(new StringBuffer(lowerCase).reverse());
+	}
+}