- Number of Islands DaleStudy#258

Author: ayosecu

number-of-islands/ayosecu.py

@@ -0,0 +1,47 @@
+from typing import List
+
+class Solution:
+    """
+        - Time Complexity: O(N), N = The number of items = len(grid) * len(grid[0])
+        - Space Complexity: O(N)
+            - In worst case (all "1"s), The depth of dfs is N => O(N)
+    """
+    def numIslands(self, grid: List[List[str]]) -> int:
+        m, n = len(grid), len(grid[0])
+
+        def dfs(i, j):
+            if i < 0 or i >= m or j < 0 or j >= n or grid[i][j] != "1":
+                return
+            
+            grid[i][j] = "#"    # Visited
+            for dx, dy in [(1, 0), (0, 1), (0, -1), (-1, 0)]:
+                dfs(i + dx, j + dy)               
+
+        count = 0            
+        for i in range(m):
+            for j in range(n):
+                if grid[i][j] == "1":
+                    count += 1
+                    dfs(i, j)
+        
+        return count
+
+tc = [
+        ([
+            ["1","1","1","1","0"],
+            ["1","1","0","1","0"],
+            ["1","1","0","0","0"],
+            ["0","0","0","0","0"]
+        ], 1),
+        ([
+            ["1","1","0","0","0"],
+            ["1","1","0","0","0"],
+            ["0","0","1","0","0"],
+            ["0","0","0","1","1"]
+        ], 3)
+]
+
+sol = Solution()
+for i, (grid, e) in enumerate(tc, 1):
+    r = sol.numIslands(grid)
+    print(f"TC {i} is Passed!" if r == e else f"TC {i} is Failed! - Expected: {e}, Result: {r}")