You are given a map in form of a two-dimensional integer grid where 1 represents land and 0 represents water. Grid cells are connected horizontally/vertically (not diagonally). The grid is completely surrounded by water, and there is exactly one island (i.e., one or more connected land cells). The island doesn't have "lakes" (water inside that isn't connected to the water around the island). One cell is a square with side length 1. The grid is rectangular, width and height don't exceed 100. Determine the perimeter of the island.

Example:

 [1,1,1,0],
 [0,1,0,0],
 [1,1,0,0]]
Answer: 16Explanation: The perimeter is the 16 yellow stripes 

想了下，其實(shí)就是每個(gè)塊都是四個(gè)邊，然后減去上下左右重復(fù)的一個(gè)邊就可以了：

    def islandPerimeter(self, grid):
        """
        :type grid: List[List[int]]
        :rtype: int
        """
        if not grid:
            return 0
        cnt = 0
        for i in range(len(grid)):
            for j in range(len(grid[0])):
                if grid[i][j] == 1:
                    cnt += 4
                    if (i > 0 and grid[i-1][j] == 1):
                        cnt -=1
                    if (j > 0 and grid[i][j-1] == 1):
                        cnt -=1
                    if (i<len(grid)-1 and grid[i+1][j] == 1):
                        cnt -=1
                    if (j<len(grid[0])-1 and grid[i][j+1] == 1):
                        cnt -=1
        
        return cnt