diff --git a/longest-substring-without-repeating-characters/naringst.py b/longest-substring-without-repeating-characters/naringst.py
new file mode 100644
index 000000000..e8af59110
--- /dev/null
+++ b/longest-substring-without-repeating-characters/naringst.py
@@ -0,0 +1,22 @@
+
+#  Runtime: 51ms, Memory: 16.83MB
+#  Time complexity: O(len(s)^2)
+#  Space complexity: O(len(s))
+
+class Solution:
+    def lengthOfLongestSubstring(self, s: str) -> int:
+        stringArr = []
+        maxLength = 0
+
+        for sub in s :
+            if sub in stringArr :    
+                maxLength = max(maxLength, len(stringArr))
+                repeatIdx = stringArr.index(sub)
+                stringArr = stringArr[repeatIdx+1 :]
+
+            stringArr.append(sub)
+        
+        maxLength = max(maxLength, len(stringArr))
+
+
+        return maxLength
diff --git a/number-of-islands/naringst.py b/number-of-islands/naringst.py
new file mode 100644
index 000000000..2e64ee693
--- /dev/null
+++ b/number-of-islands/naringst.py
@@ -0,0 +1,44 @@
+from collections import deque 
+
+#  Runtime: 241ms, Memory: 18.94MB
+#  Time complexity: O(len(n*m))
+#  Space complexity: O(len(n*m))
+
+
+class Solution:
+    def bfs(self, a,b, grid, visited) :
+        n = len(grid)
+        m = len(grid[0])
+
+        dx = [0, 0, 1, -1]
+        dy = [1, -1 ,0 ,0]
+        q = deque()
+        q.append([a,b])
+        visited[a][b] = True
+
+        while q :
+            x,y = q.popleft()
+
+            for i in range(4) :
+                nx = x + dx[i]
+                ny = y + dy[i]
+
+                if (0 <= nx  < n and 0 <= ny < m and not visited[nx][ny] and grid[nx][ny] == '1'):
+                    visited[nx][ny] = True
+                    q.append([nx,ny])
+
+
+
+    def numIslands(self, grid: List[List[str]]) -> int:
+        n = len(grid)
+        m = len(grid[0])
+        visited = [[False] * m for _ in range(n)]
+        answer = 0
+        
+        for i in range(n) :
+            for j in range(m) :
+                if grid[i][j] == '1' and not visited[i][j] :
+                    self.bfs(i,j,grid,visited)
+                    answer += 1
+
+        return answer
diff --git a/reverse-linked-list/naringst.py b/reverse-linked-list/naringst.py
new file mode 100644
index 000000000..4cde2ab75
--- /dev/null
+++ b/reverse-linked-list/naringst.py
@@ -0,0 +1,27 @@
+
+#  Runtime: 39ms, Memory: 17.88MB
+#  Time complexity: O(len(head))
+#  Space complexity: O(len(head))
+
+
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+
+class Solution:
+    def __init__(self):
+        self.nodes = []  # ListNode 객체를 저장할 배열
+
+    def reverseList(self, head: Optional[ListNode]) -> List[Optional[ListNode]]:
+        prev = None
+        curr = head
+
+        while curr is not None:
+            nextNode = curr.next
+            curr.next = prev
+            prev = curr
+            curr = nextNode
+    
+        return prev