<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 vis[105][105];
    vector<pair<int,int> >d={{0,1},{0,-1},{-1,0},{1,0}};
    int n,m;
    int prt=0;
    bool valid(int i,int j)
    {
        if(i<0 || i>=n || j<0 || j>=m)
        {
            return false;
        }
        return true;
    }
    void bfs(int si,int sj,vector<vector<int>>& grid)
    {
        queue<pair<int,int>>q;
        q.push({si,sj});
        vis[si][sj]=true;
        while(!q.empty())
        {
            pair<int,int>par = q.front();
            int a=par.first,b=par.second;
            q.pop();
            for(int i=0;i<4;++i)
            {
                int ci = a+d[i].first;
                int cj = b+d[i].second;
                if(valid(ci,cj)==true && vis[ci][cj]==false)
                {
                    q.push({ci,cj});
                    vis[ci][cj]=true;
                }
                if(valid(ci,cj)==true && grid[a][b]==1 && grid[ci][cj]==0)
                {
                    ++prt;
                }
                if(grid[a][b]==1 && valid(ci,cj)==false)
                {
                    ++prt;
                }
            }
        }
    }
    int islandPerimeter(vector<vector<int>>& grid) {
        memset(vis,false,sizeof(vis));
        n=grid.size();
        m=grid[0].size();
        bfs(0,0,grid);
        return prt;
    }
};
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