<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];
int ans;
vector<pair<int,int>>d= {{0,1},{0,-1},{1,0},{-1,0}};
int n, m;
bool valid(int ci,int cj)
{
    if(ci>=0 && ci<n && cj>=0 && cj<m) return true;
   else return false;
}
void dfs(int si, int sj, vector<vector<int>>& grid)
{
  vis[si][sj]=true;
  for(int i=0; i<4; i++)
  {
     int ci= si+d[i].first;
     int cj= sj+d[i].second;
     if(valid(ci,cj))
     {
        if(grid[ci][cj]==0) ans++;
     }
     else
     {
        ans++;
     }
     if(valid(ci,cj) && !vis[ci][cj] && grid[ci][cj]==1)
     {
        dfs(ci,cj,grid);
     }
  }
}
    int islandPerimeter(vector<vector<int>>& grid) {
      memset(vis,false,sizeof(vis));
      ans=0;
      n=grid.size();
      m=grid[0].size();
      for(int i=0; i<n;i++)
      {
        for(int j=0; j<m;j++)
        {
            if(!vis[i][j] && grid[i][j]==1)
            {
                dfs(i,j,grid);
            }
        }
      }  
      return ans;
    }
};
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