Island Perimeter

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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:

[[0,1,0,0],
[1,1,1,0],
[0,1,0,0],
[1,1,0,0]]

Answer: 16

我的思路，就是将现有的矩阵用零填充，然后先按行看，如果出现前后数字不一致则给周长加一，再按列看，上下数字不一致给周长加一。

class Solution(object):    def islandPerimeter(self, grid):        """        :type grid: List[List[int]]        :rtype: int        """        perimeter = 0        tmp = [[0 for i in range(len(grid[0])+2)]]        for i in range(len(grid)):                tmp.append([0] + grid[i] + [0])        tmp.append([0 for i in range(len(grid[0])+2)])        for i in range(len(tmp) - 1):            for j in range(len(tmp[0]) - 1):                if tmp[i][j] != tmp[i][j+1]:                    perimeter += 1                if tmp[i][j] != tmp[i+1][j]:                    perimeter += 1        return perimeter

接下来看一下大神们的解法：

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