From 35df9c2559de592673ecaebb1144f089be4b0ae4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=EC=9D=B4=EB=8F=99=ED=95=B4?= <leedonghae@day1company.co.kr>
Date: Wed, 19 Nov 2025 21:08:32 +0900
Subject: [PATCH 1/3] valid-anagram solution

---
 valid-anagram/Donghae0230.py | 13 +++++++++++++
 1 file changed, 13 insertions(+)
 create mode 100644 valid-anagram/Donghae0230.py

diff --git a/valid-anagram/Donghae0230.py b/valid-anagram/Donghae0230.py
new file mode 100644
index 0000000000..9bc78810f7
--- /dev/null
+++ b/valid-anagram/Donghae0230.py
@@ -0,0 +1,13 @@
+class Solution:
+    def isAnagram(self, s: str, t: str) -> bool:
+        s_list = sorted(list(s))
+        t_list = sorted(list(t))
+        # 1. 두 단어의 길이가 다른 경우 false 반환
+        if len(s_list) != len(t_list):
+            return False
+        else:
+            # 2. 각 알파벳의 순서가 일치하지 않는 경우 false 반환
+            for i in range(0, len(s_list)):
+                if s_list[i] != t_list[i]:
+                    return False
+            return True

From 10493754e1e78dd83bef2e9886d4b41a1d432135 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=EC=9D=B4=EB=8F=99=ED=95=B4?= <leedonghae@day1company.co.kr>
Date: Sat, 22 Nov 2025 15:21:32 +0900
Subject: [PATCH 2/3] =?UTF-8?q?2=EC=A3=BC=EC=B0=A8=20solution?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 climbing-stairs/Donghae0230.py              | 21 ++++++++++
 product-of-array-except-self/Donghae0230.py | 43 +++++++++++++++++++++
 valid-anagram/Donghae0230.py                |  2 +
 3 files changed, 66 insertions(+)
 create mode 100644 climbing-stairs/Donghae0230.py
 create mode 100644 product-of-array-except-self/Donghae0230.py

diff --git a/climbing-stairs/Donghae0230.py b/climbing-stairs/Donghae0230.py
new file mode 100644
index 0000000000..ab43068d4a
--- /dev/null
+++ b/climbing-stairs/Donghae0230.py
@@ -0,0 +1,21 @@
+# 1스텝 또는 2스텝으로 n개의 계단을 오르는 방법 경우의 수 구하기
+# 1계단: 1
+# 2계단: 2 , 1 + 1
+# 3계단: 2 + 1, 1+1+1, 1+2
+# 4계단: 2+2, 1+1+1+1, 2+1+1, 1+2+1, 1+1+2
+#  -> 방법: step_n = step_(n-1) + step_(n-2)
+# 시간 복잡도: O(n), while문 사용
+# 공간 복잡도: O(n), 길이 n인 result 리스트 생성
+class Solution:
+    def climbStairs(self, n: int) -> int:
+        if n == 1:
+            return 1
+        elif n == 2:
+            return 2
+        else:
+            result = [1, 2]
+            i = 2
+            while i < n:
+                result.append(result[i-1] + result[i-2])
+                i += 1
+            return result[-1]
\ No newline at end of file
diff --git a/product-of-array-except-self/Donghae0230.py b/product-of-array-except-self/Donghae0230.py
new file mode 100644
index 0000000000..d7b93aac21
--- /dev/null
+++ b/product-of-array-except-self/Donghae0230.py
@@ -0,0 +1,43 @@
+# 2차 시도: 왼쪽 누적 곱 * 오른쪽 누적 곱
+# 시간 복잡도: O(n), for문 사용
+# 공간 복잡도: O(n), 길이 n인 리스트 prefix, suffix, result 생성
+class Solution:
+    def productExceptSelf(self, nums: List[int]) -> List[int]:
+        # 왼쪽 누적 곱 리스트 생성
+        prefix = [nums[0]]
+        for i in range(1, len(nums)-1):
+            tmp = nums[i]
+            prefix.append(prefix[i-1] * nums[i])
+
+        nums.reverse()
+        # 오른쪽 누적 곱 리스트 생성
+        suffix = [nums[0]]
+        for i in range(1, len(nums)-1):
+            tmp = nums[i]
+            suffix.append(suffix[i-1] * nums[i])
+
+        # result[0] = suffix[2]
+        # result[1] = suffix[1] * prefix[0]
+        # result[2] = suffix[0] * prefix[1]
+        # result[3] =             prefix[2]
+        result = [0 for i in range(0, len(nums))]
+        result[0] = suffix[-1]
+        result[-1] = prefix[-1]
+        for i in range(1, len(nums)-1):
+            result[i] = suffix[len(nums)-2-i] * prefix[i-1]
+        return result
+
+
+# 1차 시도: 이중 for문 사용
+# 시간 복잡도: O(n^2)으로 실패
+# class Solution:
+#     def productExceptSelf(self, nums: List[int]) -> List[int]:
+#         result = []
+#         for i in range(0, len(nums)):
+#             tmp = 1
+#             for j in range(0, len(nums)):
+#                 if i == j:
+#                     continue
+#                 tmp *= nums[j]
+#             result.append(tmp)
+#         return result
\ No newline at end of file
diff --git a/valid-anagram/Donghae0230.py b/valid-anagram/Donghae0230.py
index 9bc78810f7..ab217a830e 100644
--- a/valid-anagram/Donghae0230.py
+++ b/valid-anagram/Donghae0230.py
@@ -1,3 +1,5 @@
+# 시간 복잡도: O(n), for문 사용
+# 공간 복잡도: O(n), 길이 n인 s_list, t_list 생성
 class Solution:
     def isAnagram(self, s: str, t: str) -> bool:
         s_list = sorted(list(s))

From a8c940acf2bf76060602cec3c6d9e7db72202f65 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=EC=9D=B4=EB=8F=99=ED=95=B4?= <leedonghae@day1company.co.kr>
Date: Sat, 22 Nov 2025 15:23:05 +0900
Subject: [PATCH 3/3] line lint

---
 climbing-stairs/Donghae0230.py              | 2 +-
 product-of-array-except-self/Donghae0230.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/climbing-stairs/Donghae0230.py b/climbing-stairs/Donghae0230.py
index ab43068d4a..20d2b08236 100644
--- a/climbing-stairs/Donghae0230.py
+++ b/climbing-stairs/Donghae0230.py
@@ -18,4 +18,4 @@ def climbStairs(self, n: int) -> int:
             while i < n:
                 result.append(result[i-1] + result[i-2])
                 i += 1
-            return result[-1]
\ No newline at end of file
+            return result[-1]
diff --git a/product-of-array-except-self/Donghae0230.py b/product-of-array-except-self/Donghae0230.py
index d7b93aac21..81d745d1ff 100644
--- a/product-of-array-except-self/Donghae0230.py
+++ b/product-of-array-except-self/Donghae0230.py
@@ -40,4 +40,4 @@ def productExceptSelf(self, nums: List[int]) -> List[int]:
 #                     continue
 #                 tmp *= nums[j]
 #             result.append(tmp)
-#         return result
\ No newline at end of file
+#         return result