Given an m×n 2D binary grid '1' (land) and '0' (water), count the number of islands. An island is surrounded by water and formed by connecting adjacent lands horizontally or vertically.
grid = [["1","1","1","1","0"],["1","1","0","1","0"],["1","1","0","0","0"],["0","0","0","0","0"]]1grid = [["1","1","0","0","0"],["1","1","0","0","0"],["0","0","1","0","0"],["0","0","0","1","1"]]3