island.py

grid = [
  ["1","1","1","1","0"],
  ["1","1","0","1","0"],
  ["1","1","0","0","0"],
  ["0","0","0","0","0"]
]
island = 0
seen = set([])
i = 0
while i < len(grid):
  j = 0
  while j < len(grid[0]):
    if (i,j) not in seen and grid[i,j] == '1':
      queue = [(i,j)]
      while queue:
        x, y = queue.pop()
        if (x, y) not in seen:
          seen.add((x,y))
          if x - 1 >= 0 and grid[x-1, y] == '1':
            queue.append((x-1, y))
          if x < len(grid) and grid[x+1, y] == '1':
            queue.append((x+1, y))
          if y - 1 >= 0 and grid[x, y-1] == '1':
            queue.append((x, y-1))
          if y < len(grid[0]) and grid[x, y+1] == '1':
            queue.append((x, y+1))
      island += 1
      j += 1
  i += 1
print(island)

[[1]]
[[0]]
[[1,0,0,1]
 [0,1,0,0],
 [0,1,0,1]]