<p>You are given <code>row x col</code> <code>grid</code> representing a map where <code>grid[i][j] = 1</code> represents&nbsp;land and <code>grid[i][j] = 0</code> represents water.</p>

<p>Grid cells are connected <strong>horizontally/vertically</strong> (not diagonally). The <code>grid</code> is completely surrounded by water, and there is exactly one island (i.e., one or more connected land cells).</p>

<p>The island doesn&#39;t have &quot;lakes&quot;, meaning the water inside isn&#39;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&#39;t exceed 100. Determine the perimeter of the island.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img src="https://assets.leetcode.com/uploads/2018/10/12/island.png" style="width: 221px; height: 213px;" />
<pre>
<strong>Input:</strong> grid = [[0,1,0,0],[1,1,1,0],[0,1,0,0],[1,1,0,0]]
<strong>Output:</strong> 16
<strong>Explanation:</strong> The perimeter is the 16 yellow stripes in the image above.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> grid = [[1]]
<strong>Output:</strong> 4
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> grid = [[1,0]]
<strong>Output:</strong> 4
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>row == grid.length</code></li>
	<li><code>col == grid[i].length</code></li>
	<li><code>1 &lt;= row, col &lt;= 100</code></li>
	<li><code>grid[i][j]</code> is <code>0</code> or <code>1</code>.</li>
	<li>There is exactly one island in <code>grid</code>.</li>
</ul>

class Solution {
public:
    int islandPerimeter(vector<vector<int>>& grid) {
        int m = grid.size(), n = grid[0].size(), res = 0;
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (grid[i][j] == 1) {
                    grid[i][j] = 2;
                    return dfs(grid, i, j);
                }
            }
        }

        return 0;
    }

    vector<vector<int>> dir = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};

    int dfs(vector<vector<int>>& grid, int y, int x) {
        int m = grid.size(), n = grid[0].size(), res = 0;
        if (y == 0) {
            res++;
        }
        if (x == 0) {
            res++;
        }
        if (y == m-1) {
            res++;
        }
         if (x == n-1) {
            res++;
        }
       // grid[y][x] = 2;
        for (const auto& v : dir) {
            int a = y + v[0], b = x + v[1];
            if (a < 0 || a >= m || b < 0 || b >= n) continue;
            if (grid[a][b] == 0) {
                res++;
            } else if (grid[a][b] == 1) {
                grid[a][b] = 2;
                res += dfs(grid, a, b);
            }
        }
       // grid[y][x] = 1;
        return res;
    }
};
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