The Solution to Leetcode 463 Island Perimeter

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本文介绍了一个算法问题，即如何计算二维网格中岛屿的周长。通过遍历每个单元格并检查相邻的水区域来确定岛屿边界的方法被详细阐述。

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Question:

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:

Answer:

class Solution {
public:
    int islandPerimeter(vector<vector<int>>& grid) {
        int i,j;
        int n=grid.size();
        if(n==0)return 0;
        int m=grid[0].size();
        if(m==0)return 0;
         int count=0;
        for(i=0;i<n;i++)
           for(j=0;j<m;j++)
             if(grid[i][j]==1)
            {
             if(i==0) count++;
             if(j==0) count++;
             if(i==n-1)count++;
             if(j==n-1) count++;
             if(i>0 && grid[i-1][j]==0) count++;
             if(i<n-1 && grid[i+1][j]==0) count++;
             if(j>0 && grid[i][j-1]==0) count++;
             if(j<m-1 && grid[i][j+1]==0) count++;
                
            }
            return count;
    }
};

run code results:

Your input

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

The Solution to Leetcode 463 Island Perimeter

run code results:

Your input

Your answer

Expected answer