463. Island Perimeter-优快云博客

本文介绍了一个算法问题：计算二维网格中岛屿的周长。网格由0和1组成，1代表陆地，0代表水域。文章提供了C++代码实现，通过遍历网格来计算岛屿的边界长度。

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:

class Solution {
public:
    int islandPerimeter(vector<vector<int>>& grid) {
        if(grid.size() == 0) return 0;
        
        int rows = grid.size();
        int columns = grid[0].size();
        
        int cnt =0;
        int repeats = 0;
        
        for(int iRow = 0;iRow < rows; iRow++){
            for(int jClo = 0;jClo < columns; jClo++){
                if(grid[iRow][jClo] == 1)
                {
                    cnt++;
                    if(iRow!=0 && grid[iRow-1][jClo] ==1) ++repeats;
                    if(jClo!=0 && grid[iRow][jClo-1] ==1) ++repeats;
                }
            }
        }
        return cnt*4-repeats*2;
    }
};