solve : number of islands

Author: SamTheKorean

number-of-islands/samthekorean.py

@@ -0,0 +1,26 @@
+# TC : O(n) where n is the number of elements in the two-dimensional list.
+# SC : O(n) where n is the depth of the stack of recursive calls.
+class Solution:
+    def numIslands(self, grid: List[List[str]]) -> int:
+        def dfs(r, c):
+            # Mark the current cell as visited by setting it to "0"
+            grid[r][c] = "0"
+            # Explore all four possible directions (right, down, left, up)
+            for dr, dc in [(0, 1), (1, 0), (0, -1), (-1, 0)]:
+                nr, nc = r + dr, c + dc
+                # Check if the new position is within bounds and is land ("1")
+                if (
+                    0 <= nr < len(grid)
+                    and 0 <= nc < len(grid[0])
+                    and grid[nr][nc] == "1"
+                ):
+                    dfs(nr, nc)
+
+        island_count = 0
+        # Traverse each cell in the grid
+        for r in range(len(grid)):
+            for c in range(len(grid[0])):
+                if grid[r][c] == "1":  # Found an island
+                    island_count += 1  # Increment the island count
+                    dfs(r, c)  # Sink the entire island
+        return island_count  # Return the total number of islands