<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>

int dir[][2] = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};

class Solution {
public:
    int expand(queue<pair<int, int>>& bfs, vector<vector<int>>& grid) {
        int perimeter = 0;
        while (!bfs.empty()) {
            auto cur = bfs.front();
            bfs.pop();

            if (grid[cur.first][cur.second] == 2) continue;
            grid[cur.first][cur.second] = 2;

            for (int i = 0; i < 4; i++) {
                int r = cur.first + dir[i][0];
                int c = cur.second + dir[i][1];
                if (r < 0 || r >= grid.size() || c < 0 || c >= grid[0].size() || grid[r][c] == 0) {
                    perimeter++;
                    continue;
                }
                if (grid[r][c] == 1) {
                    bfs.push({r, c});
                }
            }
        }
        return perimeter;
    }

    int islandPerimeter(vector<vector<int>>& grid) {
        for (int r = 0; r < grid.size(); r++) {
            for (int c = 0; c < grid[0].size(); c++) {
                if (grid[r][c] == 0) continue;
                queue<pair<int, int>> bfs;
                bfs.push({r, c});
                return expand(bfs, grid);
            }
        }
        return 0;
    }
};
73562