From 7fd6cd44efd46335709cba17c5b3c4841389837f Mon Sep 17 00:00:00 2001
From: changhyumm <kch9132@gmail.com>
Date: Mon, 1 Dec 2025 23:57:53 +0900
Subject: [PATCH 1/6] merge-two-sorted-lists

---
 merge-two-sorted-lists/changhyumm.py | 30 ++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 merge-two-sorted-lists/changhyumm.py

diff --git a/merge-two-sorted-lists/changhyumm.py b/merge-two-sorted-lists/changhyumm.py
new file mode 100644
index 0000000000..33eafe8a6c
--- /dev/null
+++ b/merge-two-sorted-lists/changhyumm.py
@@ -0,0 +1,30 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
+        # head of merged linked list를 반환해야 하므로 head를 임시로 생성
+        head = ListNode()
+        pointer = head
+
+        # 정렬된 링크드 리스트이므로 하나라도 끝까지 pointer를 이동해서 None이 될때까지 loop
+        # 시간복잡도 O(n), 공간복잡도 O(1)
+        while list1 and list2:
+            # val 비교해서 next 지정
+            if list1.val <= list2.val:
+                pointer.next = list1
+                list1 = list1.next
+            else:
+                pointer.next = list2
+                list2 = list2.next
+            # pointer도 next로 이동
+            pointer = pointer.next
+        # 남은 리스트의 경우 정렬되어 있으므로 그대로 연결
+        if list1:
+            pointer.next = list1
+        else:
+            pointer.next = list2
+
+        return head.next

From 97c514d19e33b1a1f4dfda7365e375df0f524844 Mon Sep 17 00:00:00 2001
From: changhyumm <kch9132@gmail.com>
Date: Thu, 4 Dec 2025 00:01:06 +0900
Subject: [PATCH 2/6] maximum-depth-of-binary-tree

---
 maximum-depth-of-binary-tree/changhyumm.py | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
 create mode 100644 maximum-depth-of-binary-tree/changhyumm.py

diff --git a/maximum-depth-of-binary-tree/changhyumm.py b/maximum-depth-of-binary-tree/changhyumm.py
new file mode 100644
index 0000000000..8ba1fe3d49
--- /dev/null
+++ b/maximum-depth-of-binary-tree/changhyumm.py
@@ -0,0 +1,20 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def maxDepth(self, root: Optional[TreeNode]) -> int:
+        if root is None:
+            return 0
+        stack = [[root, 1]]
+        max_depth = 1
+        while stack:
+            node, cur_depth = stack.pop()
+            max_depth = max(max_depth, cur_depth)
+            if node.left:
+                stack.append([node.left, cur_depth + 1])
+            if node.right:
+                stack.append([node.right, cur_depth + 1])
+        return max_depth
\ No newline at end of file

From 49e7491fcf5d3a669656f7c97c1f6172ef2cc6fb Mon Sep 17 00:00:00 2001
From: changhyumm <kch9132@gmail.com>
Date: Thu, 4 Dec 2025 00:26:22 +0900
Subject: [PATCH 3/6] =?UTF-8?q?=EC=A3=BC=EC=84=9D?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 maximum-depth-of-binary-tree/changhyumm.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/maximum-depth-of-binary-tree/changhyumm.py b/maximum-depth-of-binary-tree/changhyumm.py
index 8ba1fe3d49..770c0534ae 100644
--- a/maximum-depth-of-binary-tree/changhyumm.py
+++ b/maximum-depth-of-binary-tree/changhyumm.py
@@ -6,8 +6,11 @@
 #         self.right = right
 class Solution:
     def maxDepth(self, root: Optional[TreeNode]) -> int:
+        # root가 없는경우 depth 0
         if root is None:
             return 0
+        # depth를 같이 포함시킴
+        # dfs의 경우 각 경로별로 끝까지 탐색하는데, 각 경로마다 depth가 다르므로 표기하면서 stack에 추가해야함
         stack = [[root, 1]]
         max_depth = 1
         while stack:

From 967b3c3a1bacfd197309013805d87804689f1f0c Mon Sep 17 00:00:00 2001
From: changhyumm <kch9132@gmail.com>
Date: Thu, 4 Dec 2025 22:33:39 +0900
Subject: [PATCH 4/6] minimum-in-rotated-sorted-array

---
 find-minimum-in-rotated-sorted-array/changhyumm.py | 14 ++++++++++++++
 maximum-depth-of-binary-tree/changhyumm.py         |  2 +-
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 find-minimum-in-rotated-sorted-array/changhyumm.py

diff --git a/find-minimum-in-rotated-sorted-array/changhyumm.py b/find-minimum-in-rotated-sorted-array/changhyumm.py
new file mode 100644
index 0000000000..640f045b91
--- /dev/null
+++ b/find-minimum-in-rotated-sorted-array/changhyumm.py
@@ -0,0 +1,14 @@
+class Solution:
+    def findMin(self, nums: List[int]) -> int:
+        # 시간복잡도 O(logn) 제약사항이 있으므로 binary search 사용
+        left = 0
+        right = len(nums) - 1
+        # rotated sort 이므로 mid와 right 비교
+        # mid 와 left 비교시 최소값이 어딨는지 특정할 수가 없음 (예외케이스 발생)
+        while left < right:
+            mid = (left + right) // 2
+            if nums[mid] < nums[right]:
+                right = mid
+            else:
+                left = mid + 1
+        return nums[left]
diff --git a/maximum-depth-of-binary-tree/changhyumm.py b/maximum-depth-of-binary-tree/changhyumm.py
index 770c0534ae..b37bd76a04 100644
--- a/maximum-depth-of-binary-tree/changhyumm.py
+++ b/maximum-depth-of-binary-tree/changhyumm.py
@@ -20,4 +20,4 @@ def maxDepth(self, root: Optional[TreeNode]) -> int:
                 stack.append([node.left, cur_depth + 1])
             if node.right:
                 stack.append([node.right, cur_depth + 1])
-        return max_depth
\ No newline at end of file
+        return max_depth

From 1465b01850d0c8bd1bf025b52f548ac9fdbd1eb1 Mon Sep 17 00:00:00 2001
From: changhyumm <kch9132@gmail.com>
Date: Thu, 4 Dec 2025 23:42:09 +0900
Subject: [PATCH 5/6] word-search

---
 word-search/changhyumm.py | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 word-search/changhyumm.py

diff --git a/word-search/changhyumm.py b/word-search/changhyumm.py
new file mode 100644
index 0000000000..d807bd7c76
--- /dev/null
+++ b/word-search/changhyumm.py
@@ -0,0 +1,24 @@
+class Solution:
+    def exist(self, board: List[List[str]], word: str) -> bool:
+        rows, cols = len(board), len(board[0])
+        visited = set()
+
+        def dfs(row, col, idx):
+            # 끝까지 탐색시 길이와 k가 같아지므로 True 반환
+            if idx == len(word):
+                return True
+            # 범위를 벗어난 경우, 방문한 경우, 같은 word가 없는 경우 False 반환
+            if not (0 <= row < rows) or not (0 <= col < cols) or (row, col) in visited or board[row][col] != word[idx]:
+                return False
+            
+            visited.add((row, col))
+            res = dfs(row + 1, col, idx + 1) or dfs(row - 1, col, idx + 1) or dfs(row, col + 1, idx + 1) or dfs(row, col - 1, idx + 1)
+            visited.remove((row, col))
+            return res
+        # 시작점 탐색
+        for row in range(rows):
+            for col in range(cols):
+                if dfs(row, col, 0):
+                    return True
+        # 시간복잡도 O(len(row)*len(col)*4^(word))
+        return False

From f0eab025423a64faf7c6105698d3841124026afa Mon Sep 17 00:00:00 2001
From: changhyumm <kch9132@gmail.com>
Date: Thu, 4 Dec 2025 23:44:59 +0900
Subject: [PATCH 6/6] =?UTF-8?q?=EC=A3=BC=EC=84=9D?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 word-search/changhyumm.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/word-search/changhyumm.py b/word-search/changhyumm.py
index d807bd7c76..c9ecd93999 100644
--- a/word-search/changhyumm.py
+++ b/word-search/changhyumm.py
@@ -20,5 +20,6 @@ def dfs(row, col, idx):
             for col in range(cols):
                 if dfs(row, col, 0):
                     return True
-        # 시간복잡도 O(len(row)*len(col)*4^(word))
+        # 시간복잡도 O(rows*cols*4^(word))
+        # 공간복잡도 O(rows*cols)
         return False