Given a 2D grid of '1's (land) and '0's (water), count the number of islands.
Sample Input:
[["1","1","0","0","0"],["1","1","0","0","0"],["0","0","1","0","0"],["0","0","0","1","1"]]
Hints
Hint 1
Use DFS or BFS to explore each island
Hint 2
Mark visited cells to avoid recounting
Hint 3
Count connected components of '1's
