<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:
    bool is_valid(std::vector<std::vector<int>>& grid, int r, int c) {
        if (r >= 0 && r < grid.size() && c >= 0 && c < grid[0].size()) {
            if (grid[r][c] == 1 || grid[r][c]==-1)
                return true;
        }
        return false;
    }
    int bfs(std::vector<std::vector<int>>& grid, int r, int c){
        int perimeter = 0;
        std::queue<std::pair<int,int>> que;
        std::vector<std::vector<int>> directions { {1,0},{0,1},{-1,0},{0,-1}};
        que.push({r,c});
        grid[r][c]=-1;
        while(!que.empty()){
            int count=0;
            std::pair<int,int> current = que.front();
            int row = current.first;
            int col = current.second;
            que.pop();
            for(const auto& dir: directions){
                int n_r = row+dir[0];
                int n_c = col+dir[1];
                if(is_valid(grid,n_r,n_c)){
                    count++;
                    if(grid[n_r][n_c]==1){
                        que.push({n_r,n_c});
                        grid[n_r][n_c]=-1;
                    }
                }
            }
            perimeter += 4 - count;
        }
        return perimeter;

    }
    int islandPerimeter(vector<vector<int>>& grid) {
        int n_rows = grid.size();
        int n_cols = grid[0].size();
        for(int row=0; row<n_rows; ++row){
            for(int col=0; col<n_cols; ++col){
                if (grid[row][col]==1){
                    return bfs(grid,row,col);
                }
            }
        }
        return 0;

    }
};
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