Solution for Valid Palindrome #220

Author: dohyeon2

valid-palindrome/dohyeon2.java

@@ -0,0 +1,18 @@
+class Solution {
+    // TC : O(n)
+    // SC : O(1)
+    public boolean isPalindrome(String s) {
+        // Condition 1 : after converting all uppercase letters into lowercase letters
+        // and removing all non-alphanumeric characters
+        String onlyAlphaNumeric = s.toLowerCase().replaceAll("[^a-z0-9]", "");
+        int length = onlyAlphaNumeric.length();
+        for (int i = 0; i < length / 2; i++) {
+            int right = length - 1 - i;
+            int left = i;
+            // Condition 2 : it reads the same forward and backward
+            if (onlyAlphaNumeric.charAt(left) != onlyAlphaNumeric.charAt(right))
+                return false;
+        }
+        return true;
+    }
+}