From 47ba1467a23e4087565e677c04812035b6439611 Mon Sep 17 00:00:00 2001
From: Yiseul Park <omjl5123@catholic.ac.kr>
Date: Wed, 8 Jul 2026 21:48:49 +0900
Subject: [PATCH 1/2] feat: 125. Valid Palindrome solution

(cherry picked from commit d881c4df0b6226a9f1b52cb2ab9532de761f94c4)
---
 valid-palindrome/Yiseull.java | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 valid-palindrome/Yiseull.java

diff --git a/valid-palindrome/Yiseull.java b/valid-palindrome/Yiseull.java
new file mode 100644
index 000000000..f64e8668e
--- /dev/null
+++ b/valid-palindrome/Yiseull.java
@@ -0,0 +1,31 @@
+class Solution {
+    public boolean isPalindrome(String s) {
+        /**
+        첫 번째 풀이: 시간복잡도 O(n), 공간복잡도 O(n)
+        String letters = s.replaceAll("[^a-zA-Z0-9]", "").toLowerCase();
+        String reverse = new StringBuilder(letters).reverse().toString();
+        return letters.equals(reverse);
+         */
+
+        // 두 번째 풀이: 시간복잡도 O(n), 공간복잡도 O(1)
+         int left = 0, right = s.length() - 1;
+         while (left < right) {
+            while (left < right && !Character.isLetterOrDigit(s.charAt(left))) {
+                left++;
+            }
+
+            while (left < right && !Character.isLetterOrDigit(s.charAt(right))) {
+                right--;
+            }
+
+            if (Character.toLowerCase(s.charAt(left)) != Character.toLowerCase(s.charAt(right))) {
+                return false;
+            }
+
+            left++;
+            right--;
+         }
+
+         return true;
+    }
+}

From 3ba4012055f492b34d5317354f6b727cbbeda181 Mon Sep 17 00:00:00 2001
From: Yiseul Park <omjl5123@catholic.ac.kr>
Date: Wed, 8 Jul 2026 22:44:46 +0900
Subject: [PATCH 2/2] feat: 191. Number of 1 Bits solution

---
 number-of-1-bits/Yiseull.java | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 number-of-1-bits/Yiseull.java

diff --git a/number-of-1-bits/Yiseull.java b/number-of-1-bits/Yiseull.java
new file mode 100644
index 000000000..921cc140e
--- /dev/null
+++ b/number-of-1-bits/Yiseull.java
@@ -0,0 +1,5 @@
+class Solution {
+    public int hammingWeight(int n) {
+        return Integer.bitCount(n);
+    }
+}