200. Number of Islands

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
00000
Output: 1

Example 2:
Input:
11000
11000
00100
00011
Output: 3

题目大意：给定一个2维数组，0代表水，1代表陆地，求岛屿的数量，相邻的陆地算一个岛屿。
比如：

class Solution(object):
    def numIslands(self, grid):
        """
        :type grid: List[List[str]]
        :rtype: int
        """
        count = 0
        for i in range(len(grid)):
            for j in range(len(grid[0])):
                if grid[i][j] == "1":
                    self.doBfs(grid, i, j)
                    count += 1
        return count



    def doBfs(self, grid, i, j):
        dep = []
        dep.append([i, j])
        while dep:
            x, y = dep.pop()
            grid[x][y] = "v"
            if x + 1 < len(grid) and grid[x + 1][y] == "1":
                dep.append([x+1, y])
            if y + 1 < len(grid[0]) and grid[x][y + 1] == "1":
                dep.append([x, y + 1])
            if x - 1 >= 0 and grid[x - 1][y] == "1":
                dep.append([x - 1, y])
            if y - 1 >= 0 and grid[x][y - 1] == "1":
                dep.append([x, y - 1])