463. Island Perimeter

最新推荐文章于 2019-09-24 10:24:09 发布

转载最新推荐文章于 2019-09-24 10:24:09 发布 · 66 阅读

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原文链接：http://www.cnblogs.com/gsz-/p/9489462.html

本文介绍了一个二维网格中计算岛屿周长的问题，通过暴力枚举的方法，遍历每个单元格，判断其是否为陆地并计算周边相邻陆地的数量，以此确定岛屿的总周长。

题目描述：

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:

解题思路：

暴力枚举。

代码：

 1 class Solution {
 2 public:
 3     int islandPerimeter(vector<vector<int>>& grid) {
 4         int ret = 0;
 5         for (int i = 0; i < grid.size(); ++i) {
 6             for (int j = 0; j < grid[0].size(); ++j) {
 7                 if (!grid[i][j])
 8                     continue;
 9                 int len = 4;
10                 if (i>0&&grid[i-1][j])
11                     len--;
12                 if (i<grid.size()-1&&grid[i+1][j])
13                     len--;
14                 if (j>0&&grid[i][j-1])
15                     len--;
16                 if (j<grid[0].size()-1&&grid[i][j+1])
17                     len--;
18                 ret += len;
19             }
20         }
21         return ret;
22     }
23 };