diff --git a/coin-change/daiyongg-kim.py b/coin-change/daiyongg-kim.py
new file mode 100644
index 0000000000..f1b51a9004
--- /dev/null
+++ b/coin-change/daiyongg-kim.py
@@ -0,0 +1,26 @@
+class Solution:
+    def coinChange(self, coins: List[int], amount: int) -> int:
+        if amount == 0:
+            return 0
+        
+        level = [0]
+        visited = {0}
+        count = 0
+
+        while level:
+            count += 1
+            next_level = []
+
+            for current_amount in level:
+                for coin in coins:
+                    new_amount = current_amount + coin
+
+                    if new_amount == amount:
+                        return count
+                    
+                    if new_amount < amount and new_amount not in visited:
+                        visited.add(new_amount)
+                        next_level.append(new_amount)
+            level = next_level
+
+        return -1
diff --git a/find-minimum-in-rotated-sorted-array/daiyongg-kim.py b/find-minimum-in-rotated-sorted-array/daiyongg-kim.py
new file mode 100644
index 0000000000..110de379e0
--- /dev/null
+++ b/find-minimum-in-rotated-sorted-array/daiyongg-kim.py
@@ -0,0 +1,14 @@
+class Solution:
+    def findMin(self, nums: List[int]) -> int:
+        #constraint complexity: O(log n)
+        left = 0
+        right = len(nums) - 1
+
+        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/daiyongg-kim.py b/maximum-depth-of-binary-tree/daiyongg-kim.py
new file mode 100644
index 0000000000..c31ce33f1c
--- /dev/null
+++ b/maximum-depth-of-binary-tree/daiyongg-kim.py
@@ -0,0 +1,27 @@
+class Solution:
+
+    def maxDepth(self, root: Optional[TreeNode]) -> int:
+        if not root:
+            return 0
+        queue = deque([root])
+        depth = 0
+
+        while queue:
+            depth += 1
+            print(len(queue))
+            for _ in range(len(queue)):
+                node = queue.popleft()
+                if node.left:
+                    queue.append(node.left)
+                if node.right:
+                    queue.append(node.right)
+        return depth
+
+
+#        if not root:
+#            return 0
+        
+#        left_depth = self.maxDepth(root.left)
+#        right_depth = self.maxDepth(root.right)
+
+#        return max(left_depth, right_depth) + 1
diff --git a/merge-two-sorted-lists/daiyongg-kim.py b/merge-two-sorted-lists/daiyongg-kim.py
new file mode 100644
index 0000000000..aacc307de7
--- /dev/null
+++ b/merge-two-sorted-lists/daiyongg-kim.py
@@ -0,0 +1,38 @@
+# 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]:
+        if list1 is None:
+            return list2
+        if list2 is None:
+            return list1
+        
+        if list1.val < list2.val:
+            list1.next = self.mergeTwoLists(list1.next, list2)
+            return list1
+        else: 
+            list2.next = self.mergeTwoLists(list1, list2.next)
+            return list2
+
+# class Solution:
+#     def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
+#         result = ListNode(-1)
+#         dummy = result
+#         while list1 and list2:
+#             if list1.val < list2.val:
+#                 dummy.next = list1
+#                 list1 = list1.next
+#             else:
+#                 dummy.next = list2
+#                 list2 = list2.next
+#             dummy = dummy.next
+        
+#         if list1:
+#             dummy.next = list1
+#         else:
+#             dummy.next = list2
+    
+#         return result.next
diff --git a/word-search/daiyongg-kim.py b/word-search/daiyongg-kim.py
new file mode 100644
index 0000000000..37428225ea
--- /dev/null
+++ b/word-search/daiyongg-kim.py
@@ -0,0 +1,28 @@
+class Solution:
+        
+    def exist(self, board: List[List[str]], word: str) -> bool:
+        row = len(board)
+        col = len(board[0])
+
+        def dfs(i: int, j: int, k: int):
+            if k == len(word):
+                return True
+            
+            if i < 0 or i >= row or j < 0 or j >= col or board[i][j] != word[k]:
+                return False
+
+            current = board[i][j]
+            board[i][j] = ''
+
+            if dfs(i-1, j, k+1) or dfs(i+1, j, k+1) or dfs(i, j-1, k+1) or dfs(i, j+1, k+1):
+                return True
+            
+            board[i][j] = current
+            return False
+
+        for i in range(row):
+            for j in range(col):
+                if dfs(i, j, 0):
+                    return True
+        
+        return False