Sandbox::https://github.com/coder2004/leetcode/blob/master/algorithms/python/NumberOfIslands/numIslands.py

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def numIslands(self, grid):

if not grid or not grid[0]: return 0

row, col = len(grid), len(grid[0])

self.visited = [[False for _ in range(col)] for _ in range(row)]

def floodfill(i, j):

if grid[i][j] == '1' and self.visited[i][j] == False:

self.visited[i][j] = True

if i > 0:

floodfill(i - 1, j)

if i < row - 1:

floodfill(i + 1, j)

if j > 0:

floodfill(i, j - 1)

if j < col - 1:

floodfill(i, j + 1)

res = 0

for i in range(row):

for j in range(col):

if grid[i][j] == '1' and self.visited[i][j] == False:

res += 1

floodfill(i, j)

return res