[leetcode: Python]463. Island Perimeter

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
Explanation: The perimeter is the 16 yellow stripes in the image below:

方法一：276ms

class Solution(object):    def islandPerimeter(self, grid):        """        :type grid: List[List[int]]        :rtype: int        """        height = len(grid)        weight = len(grid[0]) if height else 0        ans = 0        for h in range(height):            for w in range(weight):                if grid[h][w] == 1:                    ans += 4                    if h > 0 and grid[h-1][w]:                        ans -= 2                    if w > 0 and grid[h][w-1]:                        ans -= 2        return ans

方法二：212ms

class Solution(object):    def islandPerimeter(self, grid):        """        :type grid: List[List[int]]        :rtype: int        """        perimeter = 0        height = len(grid)        if height:            width = len(grid[0])        for i in xrange(height):            for j in xrange(width):                if grid[i][j]:                    if i and j and grid[i-1][j] and grid[i][j-1]:                        pass                    elif (not i or grid[i-1][j] == 0) and (not j or grid[i][j-1] == 0):                        perimeter += 4                    else:                        perimeter += 2        return perimeter