From 141b5308aeaf7c446f560a73be153e34eddfebc7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=EC=97=BC=ED=98=9C=EC=A0=95?=
 <122238744+cyzlcyzl@users.noreply.github.com>
Date: Tue, 6 Oct 2026 22:40:21 +0900
Subject: [PATCH] Create 125. Valid Palindrome.java

---
 .../125. Valid Palindrome.java"               | 29 +++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 "leetcode3/\354\227\274\355\230\234\354\240\225/125. Valid Palindrome.java"

diff --git "a/leetcode3/\354\227\274\355\230\234\354\240\225/125. Valid Palindrome.java" "b/leetcode3/\354\227\274\355\230\234\354\240\225/125. Valid Palindrome.java"
new file mode 100644
index 00000000..52cef60b
--- /dev/null
+++ "b/leetcode3/\354\227\274\355\230\234\354\240\225/125. Valid Palindrome.java"	
@@ -0,0 +1,29 @@
+// 투포인터
+// O(n)
+
+class Solution {
+    public boolean isPalindrome(String s) {
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i<s.length(); i++) {
+            char c = Character.toLowerCase(s.charAt(i));
+            if (isLetter(c) || isNumber(c)) sb.append(c);
+        }
+        
+        int left = 0;
+        int right = sb.length() -1;
+        while (left<right) {
+            if (sb.charAt(left) != sb.charAt(right)) return false;
+            left++;
+            right--;
+        }
+        return true;
+    }
+
+    boolean isLetter(int ord) {
+        return ord>=97 && ord <=122;
+    }
+
+    boolean isNumber(int ord) {
+        return ord>=48 && ord <=57;
+    }
+}