leetcode 463. Island Perimeter

很难坚持啊，一题要好长时间.......

不搞什么虚的了，还是尽量坚持下去.....

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:

如果一个方块是1则加4,考虑可能有相邻的边导致多加，一个格子如果有一个邻居，则相邻的边会加两次。因此，遇到1的格子，要加4减相邻的1格子数。分别考虑为1的小方块的上下左右。。。。。。。

#coding=utf-8
class Solution(object):
    def islandPerimeter(self,grid):
        """
            :type grid: List[List[int]]
            :rtype: int
            """
        if len(grid)==0 or not grid:return

        count=0;rowlength=len(grid);collength=len(grid[0])
        for i in range(rowlength):
            for j in range(collength):
                if grid[i][j]==1:
                    count+=4
                    if i>0 and grid[i-1][j]==1:#考虑上
                        count-=1
                    if i<rowlength-1 and grid[i+1][j]==1:#考虑下
                        count-=1
                    if j>0 and grid[i][j-1]==1:#考虑左
                        count-=1
                    if j<collength-1 and grid[i][j+1]==1:#考虑右
                        count-=1
        return count