# LeetCode - 0463. Island Perimeter
### 題目網址：https://leetcode.com/problems/island-perimeter/
###### tags: `LeetCode` `Easy`

/*
    -LeetCode format-
    Problem: 463. Island Perimeter
    Difficulty: Easy
    
    by Inversionpeter
*/



class Solution {
    
    #define InRange(x, y) (0 <= x && x < grid[i].size() && 0 <= y && y < grid.size())
    
    int dx[4] = { -1, 0, 1, 0 }, dy[4] = { 0, -1, 0, 1 };
    
public:
    int islandPerimeter(vector<vector<int>>& grid) {
        if (!grid.size())
            return 0;
        int perimeter = 0, land, newX, newY;
        for (int i = 0; i != grid.size(); ++i) 
            for (int j = 0; j != grid[i].size(); ++j) 
                if (grid[i][j]) {
                    land = 0;
                    for (int k = 0; k < 4; ++k) {
                        newX = j + dx[k], newY = i + dy[k];
                        if (InRange(newX, newY) && grid[newY][newX])
                            ++land;
                    }
                    perimeter += (4 - land);
                }
        return perimeter;
    }
};