Island Perimeter (LeetCode) | Algorithm Explanation

IslandPerimeter.cpp

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