[Easy] Title: 125. Valid Palindrome - LeetCode

Author: JinHyung-dev

LeetCode/Easy/125. Valid Palindrome/README.md

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+# [Easy] 26. Remove Duplicates from Sorted Array 
+
+[문제 링크](https://leetcode.com/problems/valid-palindrome/)
+
+### 문제 설명
+A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.
+
+Given a string s, return true if it is a palindrome, or false otherwise.
+
+### 입출력
+Example 1:
+```
+Input: s = "A man, a plan, a canal: Panama"
+Output: true
+```
+Explanation: "amanaplanacanalpanama" is a palindrome.
+
+Example 2:
+```
+Input: s = "race a car"
+Output: false
+```
+Explanation: "raceacar" is not a palindrome.
+
+Example 3:
+```
+Input: s = " "
+Output: true
+```
+Explanation: s is an empty string "" after removing non-alphanumeric characters.
+Since an empty string reads the same forward and backward, it is a palindrome.
+
+### 문제설명
+Constraints:
+- 1 <= s.length <= 2 * 105
+- s consists only of printable ASCII characters.

LeetCode/Easy/125. Valid Palindrome/Valid Palindrome.java

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+class Solution {
+    public boolean isPalindrome(String s) {
+        if(s == null || s.trim().isEmpty()) return true;
+
+        s = s.trim().toLowerCase().replaceAll("[^a-zA-Z0-9]+", "");
+        int left = 0; int right = s.length() - 1;
+        while(left < right) {
+            if(s.charAt(left) != s.charAt(right)) return false;
+            right--;
+            left++;
+        }
+
+        return true;
+    }
+}