Leetcode学习（11）—— Island Perimeter

最新推荐文章于 2022-04-16 22:32:35 发布

HeatDeath

最新推荐文章于 2022-04-16 22:32:35 发布

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分类专栏： Leetcode 文章标签： leetcode 地图

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本文介绍了一种计算二维网格中岛屿周长的方法。该方法通过遍历每个网格单元，检查四周相邻单元来确定周长。适用于宽度和高度不超过100的矩形网格。

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

这里写图片描述

思路：
如果格子的一条边介于陆地和海水之间，则此边为边界（周长+1）

class Solution(object):
    def islandPerimeter(self, grid):
        res = 0
        for i in range(len(grid)):
            # print('-----------------')
            # print('i:', i)
            for j in range(len(grid[i])):
                # print('j:', j)
                if grid[i][j]:
                    # 上
                    if i - 1 < 0:
                        res += 1
                    elif grid[i-1][j] == 0:
                        res += 1
                    # 左
                    if j - 1 < 0:
                        res += 1
                    elif grid[i][j-1] == 0:
                        res += 1
                    # 下
                    if i + 1 > len(grid)-1:
                        res += 1
                    elif grid[i+1][j] == 0:
                        res += 1
                    # 右
                    if j + 1 > len(grid[i])-1:
                        res += 1
                    elif grid[i][j+1] == 0:
                        res += 1
        return res

这里写图片描述