number-of-islands

Author: i-mprovising

number-of-islands/i-mprovising.py

@@ -0,0 +1,32 @@
+class Solution:
+    """
+    Time, Space comlexity O(n*m)
+    
+    connected components
+    dfs, bfs
+    """
+    def numIslands(self, grid: List[List[str]]) -> int:
+        n, m = len(grid), len(grid[0])
+        visited = [[False for _ in range(m)] for _ in range(n)] # visited 대신 grid를 0으로 표시할수도 있다
+        islands = 0
+    
+        def dfs(x, y):
+            stack = [(x, y)]
+            while stack:
+                x, y = stack.pop()
+                dx = [-1, 1, 0, 0]
+                dy = [0, 0, -1, 1]
+                for k in range(4):
+                    nx, ny = x + dx[k], y + dy[k]
+                    if 0<=nx<=n-1 and 0<=ny<=m-1:
+                        if not visited[nx][ny] and grid[nx][ny] == "1":
+                            visited[nx][ny] = True
+                            stack.append((nx, ny))
+
+        for i in range(n):
+            for j in range(m):
+                if not visited[i][j] and grid[i][j] == "1":
+                    dfs(i, j)
+                    islands += 1
+
+        return islands