From d9bc50ba7c1a080dff83385dae605a2c9708da16 Mon Sep 17 00:00:00 2001
From: Jeongwon Na <jeongwon.na@tum.de>
Date: Wed, 12 Aug 2026 13:46:37 +0200
Subject: [PATCH 1/3] solve: reverse bits

---
 reverse-bits/njngwn.py | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
 create mode 100644 reverse-bits/njngwn.py

diff --git a/reverse-bits/njngwn.py b/reverse-bits/njngwn.py
new file mode 100644
index 0000000000..1f15c8f93a
--- /dev/null
+++ b/reverse-bits/njngwn.py
@@ -0,0 +1,15 @@
+class Solution:
+    # Time Complexity: O(1)
+    # Space Complexity: O(1)
+    def reverseBits(self, n: int) -> int:
+        stack = []
+        for i in range(32):
+            stack.append(n % 2)
+            n //= 2
+
+        res, multiples = 0, 1
+        while stack:
+            res += (stack.pop() * multiples)
+            multiples *= 2
+
+        return res

From 79b80ff4001e62356a90a85ce7f84aaa2f1ed47c Mon Sep 17 00:00:00 2001
From: Jeongwon Na <jeongwon.na@tum.de>
Date: Thu, 13 Aug 2026 15:13:59 +0200
Subject: [PATCH 2/3] solve: longest repeating character replacement

---
 .../njngwn.py                                 | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)
 create mode 100644 longest-repeating-character-replacement/njngwn.py

diff --git a/longest-repeating-character-replacement/njngwn.py b/longest-repeating-character-replacement/njngwn.py
new file mode 100644
index 0000000000..ec80c6374c
--- /dev/null
+++ b/longest-repeating-character-replacement/njngwn.py
@@ -0,0 +1,21 @@
+class Solution:
+    # Time Complexity: O(n), n: len(s)
+    # Space Complexity: O(1)
+    def characterReplacement(self, s: str, k: int) -> int:
+        count = [0] * 26
+        max_len, max_cnt = 0, 0
+        left = 0
+
+        for right in range(len(s)):  # window expands
+            ch = ord(s[right]) - ord('A')
+            count[ch] += 1
+            max_cnt = max(max_cnt, count[ch])
+
+            # len(substring) - len(most frequent character) > k => window needs to schrink
+            if (right - left + 1) - max_cnt > k:
+                count[ord(s[left]) - ord('A')] -= 1
+                left += 1
+
+            max_len = max(max_len, right - left + 1)
+
+        return max_len

From 129c6b3699aae80e3d9e77f5e3f0c33eecdb986f Mon Sep 17 00:00:00 2001
From: Jeongwon Na <jeongwon.na@tum.de>
Date: Sun, 16 Aug 2026 15:09:45 +0200
Subject: [PATCH 3/3] solve: palindrome substrings

---
 palindromic-substrings/njngwn.py | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 palindromic-substrings/njngwn.py

diff --git a/palindromic-substrings/njngwn.py b/palindromic-substrings/njngwn.py
new file mode 100644
index 0000000000..bf9a2f6a40
--- /dev/null
+++ b/palindromic-substrings/njngwn.py
@@ -0,0 +1,22 @@
+class Solution:
+    # Time Complexity: O(n^2), n: len(s)
+    # Space Complexity: O(1)
+    def countSubstrings(self, s: str) -> int:
+        cnt = 0
+
+        for i in range(len(s)):
+            # odd number
+            start, end = i, i
+            while start >= 0 and end < len(s) and s[start] == s[end]:
+                start -= 1
+                end += 1
+                cnt += 1
+
+            # even number
+            start, end = i, i + 1
+            while start >= 0 and end < len(s) and s[start] == s[end]:
+                start -= 1
+                end += 1
+                cnt += 1
+
+        return cnt