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