feat(work): add solutions for number-of-islands, pacific-atlantic-water-flow, and clone-graph problems

work/1/Medium/Array/200.number-of-islands.py

@@ -12,7 +12,7 @@ An island is surrounded by water and is formed by connecting adjacent
 lands horizontally or vertically. You may assume all four edges of the
 grid are all surrounded by water.
 
- 
+
 
 Example 1:
 
@@ -34,19 +34,39 @@ Input: grid = [
 ]
 Output: 3
 
- 
+
 
 Constraints:
 
-	• m == grid.length
+        • m == grid.length
 
-	• n == grid[i].length
+        • n == grid[i].length
 
-	• 1 <= m, n <= 300
+        • 1 <= m, n <= 300
 
-	• grid[i][j] is '0' or '1'.
+        • grid[i][j] is '0' or '1'.
 """
 
+
 class Solution:
     def numIslands(self, grid: List[List[str]]) -> int:
-        
+        rows, cols = len(grid), len(grid[0])
+
+        def dfs(r, c):
+            if r < 0 or r >= rows or c < 0 or c >= cols or grid[r][c] != "1":
+                return
+            else:
+                grid[r][c] = "0"
+                dfs(r, c + 1)  # right
+                dfs(r + 1, c)  # bottom
+                dfs(r, c - 1)  # left
+                dfs(r - 1, c)  # top
+
+        num_islands = 0
+        for r in range(rows):
+            for c in range(cols):
+                if grid[r][c] == "1":
+                    num_islands += 1
+                    dfs(r, c)
+
+        return num_islands

work/1/Medium/Array/417.pacific-atlantic-water-flow.py

@@ -0,0 +1,75 @@
+"""
+417. Pacific Atlantic Water Flow
+Difficulty: Medium
+https://leetcode.com/problems/pacific-atlantic-water-flow/
+
+──────────────────────────────────────────────────
+
+There is an m x n rectangular island that borders both the Pacific
+Ocean and Atlantic Ocean. The Pacific Ocean touches the island's left
+and top edges, and the Atlantic Ocean touches the island's right and
+bottom edges.
+
+The island is partitioned into a grid of square cells. You are given
+an m x n integer matrix heights where heights[r][c] represents the
+height above sea level of the cell at coordinate (r, c).
+
+The island receives a lot of rain, and the rain water can flow to
+neighboring cells directly north, south, east, and west if the
+neighboring cell's height is less than or equal to the current cell's
+height. Water can flow from any cell adjacent to an ocean into the
+ocean.
+
+Return a 2D list of grid coordinates result where result[i] = [ri,
+ci] denotes that rain water can flow from cell (ri, ci) to both the
+Pacific and Atlantic oceans.
+
+ 
+
+Example 1:
+
+Input: heights =
+[[1,2,2,3,5],[3,2,3,4,4],[2,4,5,3,1],[6,7,1,4,5],[5,1,1,2,4]]
+Output: [[0,4],[1,3],[1,4],[2,2],[3,0],[3,1],[4,0]]
+Explanation: The following cells can flow to the Pacific and Atlantic
+oceans, as shown below:
+[0,4]: [0,4] -> Pacific Ocean 
+       [0,4] -> Atlantic Ocean
+[1,3]: [1,3] -> [0,3] -> Pacific Ocean 
+       [1,3] -> [1,4] -> Atlantic Ocean
+[1,4]: [1,4] -> [1,3] -> [0,3] -> Pacific Ocean 
+       [1,4] -> Atlantic Ocean
+[2,2]: [2,2] -> [1,2] -> [0,2] -> Pacific Ocean 
+       [2,2] -> [2,3] -> [2,4] -> Atlantic Ocean
+[3,0]: [3,0] -> Pacific Ocean 
+       [3,0] -> [4,0] -> Atlantic Ocean
+[3,1]: [3,1] -> [3,0] -> Pacific Ocean 
+       [3,1] -> [4,1] -> Atlantic Ocean
+[4,0]: [4,0] -> Pacific Ocean 
+       [4,0] -> Atlantic Ocean
+Note that there are other possible paths for these cells to flow to
+the Pacific and Atlantic oceans.
+
+Example 2:
+
+Input: heights = [[1]]
+Output: [[0,0]]
+Explanation: The water can flow from the only cell to the Pacific and
+Atlantic oceans.
+
+ 
+
+Constraints:
+
+	• m == heights.length
+
+	• n == heights[r].length
+
+	• 1 <= m, n <= 200
+
+	• 0 <= heights[r][c] <= 10^5
+"""
+
+class Solution:
+    def pacificAtlantic(self, heights: list[list[int]]) -> list[list[int]]:
+