[WEEK7]

number-of-islands solution

Author: sun912

number-of-islands/sun912.py

@@ -0,0 +1,26 @@
+"""
+    TC: O(m*n)
+    SC: O(m*n)
+"""
+class Solution:
+    def numIslands(self, grid: List[List[str]]) -> int:
+        def dfs(i, j):
+            if i < 0 or j < 0 or i >= len(grid) or j >= len(grid[0]) or grid[i][j] == "-1" or grid[i][j] == "0":
+                return
+
+            grid[i][j] = "-1"
+            dfs(i+1, j)
+            dfs(i, j+1)
+            dfs(i-1, j)
+            dfs(i, j-1)
+
+        if not grid:
+            return 0
+
+        count = 0
+        for i in range(len(grid)):
+            for j in range(len(grid[0])):
+                if grid[i][j] == "1":
+                    count += 1
+                    dfs(i, j)
+        return count