Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.
Example 1:
Input:11110 11010 11000 00000Output: 1
Example 2:
Input:11000 11000 00100 00011Output: 3
class Solution: def numIslands(self, grid: List[List[str]]) -> int: if not grid: return 0 nr, nc = len(grid), len(grid[0]) ones = set() for i in range(nr): for j in range(nc): if grid[i][j] == '1': ones.add((i,j)) moves = [(1, 0), (0, 1), (-1, 0), (0, -1)] seen = set() n_island = 0 for node in ones: if node not in seen: # new network seen.add(node) queue = [node] for ele in queue: r, c = ele for dr, dc in moves: row, col = r + dr, c + dc if (row, col) in ones and (row, col) not in seen: queue.append((row, col)) seen.add((row, col)) n_island += 1 return n_island
