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[sejineer] Week 07 solutions #1475

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May 18, 2025
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21 changes: 21 additions & 0 deletions longest-substring-without-repeating-characters/sejineer.py
Original file line number Diff line number Diff line change
@@ -0,0 +1,21 @@
"""
시간 복잡도: O(N)
공간 복잡도: O(N)
"""
class Solution:
def lengthOfLongestSubstring(self, s: str) -> int:
s_set = set()
start, end = 0, 0

result = 0

while end < len(s):
if s[end] in s_set:
s_set.remove(s[start])
start += 1
else:
s_set.add(s[end])
end += 1
result = max(result, end - start)

return result
35 changes: 35 additions & 0 deletions number-of-islands/sejineer.py
Original file line number Diff line number Diff line change
@@ -0,0 +1,35 @@
"""
시간 복잡도: O(m * n)
공간 복잡도: O(m * n)
"""
from collections import deque

class Solution:
def numIslands(self, grid: List[List[str]]) -> int:
m, n = len(grid), len(grid[0])
vis = [[False] * n for _ in range(m)]

dx = [1, -1, 0, 0]
dy = [0, 0, 1, -1]

result = 0
for i in range(m):
for j in range(n):
if grid[i][j] == '1' and not vis[i][j]:
queue = deque()
queue.append((j, i))
vis[i][j] = True
while queue:
cur = queue.popleft()
for nxt in range(4):
nx = cur[0] + dx[nxt]
ny = cur[1] + dy[nxt]
if not 0 <= nx < n or not 0 <= ny < m:
continue
if vis[ny][nx] or grid[ny][nx] != '1':
continue
queue.append((nx, ny))
vis[ny][nx] = True
result += 1

return result
15 changes: 15 additions & 0 deletions reverse-linked-list/sejineer.py
Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
"""
시간 복잡도: O(N)
공간 복잡도: O(1)
"""
class Solution:
def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
prev = None

while head:
nxt = head.next
head.next = prev
prev = head
head = nxt

return prev