Merge pull request #1882 from devyejin/main

[devyejin] WEEK 07 solutions

Author: devyejin

number-of-islands/devyejin.py

@@ -0,0 +1,31 @@
+from collections import deque
+from typing import List
+
+class Solution:
+    def numIslands(self, grid: List[List[str]]) -> int:
+        def bfs(x, y):
+            queue = deque([(x, y)])
+            grid[x][y] = "0"
+
+            while queue:
+                r, c = queue.popleft()
+
+                for d in range(4):
+                    nr, nc = r + dr[d], c + dc[d]
+                    if 0 <= nr < n and 0 <= nc < m and grid[nr][nc] == "1":
+                        grid[nr][nc] = "0"
+                        queue.append((nr, nc))
+
+        n, m = len(grid), len(grid[0])
+
+        dr = (-1, 1, 0, 0)
+        dc = (0, 0, -1, 1)
+
+        result = 0
+        for r in range(n):
+            for c in range(m):
+                if grid[r][c] == '1':
+                    bfs(r, c)
+                    result += 1
+
+        return result

set-matrix-zeroes/devyejin.py

@@ -0,0 +1,20 @@
+from typing import List
+class Solution:
+    def setZeroes(self, matrix: List[List[int]]) -> None:
+        """
+        Do not return anything, modify matrix in-place instead.
+        """
+        n, m = len(matrix), len(matrix[0])
+        rows, cols = set(), set()
+
+        for r in range(n):
+            for c in range(m):
+                if matrix[r][c] == 0:
+                    rows.add(r)
+                    cols.add(c)
+
+        for r in range(n):
+            for c in range(m):
+                if r in rows or c in cols:
+                    matrix[r][c] = 0
+

unique-paths/devyejin.py

@@ -0,0 +1,11 @@
+# 시간 복잡도 O(mn), 공간복잡도 O(mn)
+class Solution:
+    def uniquePaths(self, m: int, n: int) -> int:
+        dp = [[1] * n for _ in range(m)]
+
+        for i in range(1, m):
+            for j in range(1, n):
+                dp[i][j] = dp[i - 1][j] + dp[i][j - 1]
+
+        return dp[m - 1][n - 1]
+