<p>Given an <code>m x n</code> 2D binary grid <code>grid</code> which represents a map of <code>&#39;1&#39;</code>s (land) and <code>&#39;0&#39;</code>s (water), return <em>the number of islands</em>.</p>

<p>An <strong>island</strong> is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> grid = [
  [&quot;1&quot;,&quot;1&quot;,&quot;1&quot;,&quot;1&quot;,&quot;0&quot;],
  [&quot;1&quot;,&quot;1&quot;,&quot;0&quot;,&quot;1&quot;,&quot;0&quot;],
  [&quot;1&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;],
  [&quot;0&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;]
]
<strong>Output:</strong> 1
</pre>

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

<pre>
<strong>Input:</strong> grid = [
  [&quot;1&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;],
  [&quot;1&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;],
  [&quot;0&quot;,&quot;0&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;],
  [&quot;0&quot;,&quot;0&quot;,&quot;0&quot;,&quot;1&quot;,&quot;1&quot;]
]
<strong>Output:</strong> 3
</pre>

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

<ul>
	<li><code>m == grid.length</code></li>
	<li><code>n == grid[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 300</code></li>
	<li><code>grid[i][j]</code> is <code>&#39;0&#39;</code> or <code>&#39;1&#39;</code>.</li>
</ul>

class Solution {
public:
    int numIslands(vector<vector<char>>& grid) {
        int m=grid.size();
        int n=grid[0].size();
        int ans=0;
        // vector<vector<bool>> vis(m,vector<bool>(n,false));
        for(int i=0; i<m; i++)
        {
            for(int j=0; j<n; j++)
            {
                if(grid[i][j]=='1')
                {
                    ans++;
                    queue<vector<int>> pos;
                    pos.push({i,j});
                    while(!pos.empty())
                    {
                        int row=pos.front()[0];
                        int col=pos.front()[1];
                        pos.pop();
                        if(grid[row][col]=='0' )
                        {
                            continue;
                        }
                        grid[row][col]='0';
                        if(row+1<m && grid[row+1][col]=='1') pos.push({row+1,col});
                        if(col+1<n && grid[row][col+1]=='1') pos.push({row,col+1});
                        if(row-1>=0 && grid[row-1][col]=='1') pos.push({row-1,col});
                        if(col-1>=0 && grid[row][col-1]=='1') pos.push({row,col-1});
                    }
                }
            }
        }

        return ans;
        
    }
};


// class Solution {
// public:
//     int numIslands(vector<vector<char>>& grid) {
//         int m=grid.size();
//         int n=grid[0].size();
//         int ans=0;
//         vector<vector<bool>> vis(m,vector<bool>(n,false));
//         for(int i=0; i<m; i++)
//         {
//             for(int j=0; j<n; j++)
//             {
//                 if(grid[i][j]=='1' && vis[i][j]==false)
//                 {
//                     ans++;
//                     queue<vector<int>> pos;
//                     pos.push({i,j});
//                     while(!pos.empty())
//                     {
//                         int row=pos.front()[0];
//                         int col=pos.front()[1];
//                         pos.pop();
//                         if(row<0 || row>=m || col<0 || col>=n || grid[row][col]=='0' || vis[row][col]==true)
//                         {
//                             continue;
//                         }
//                         vis[row][col]=true;
//                         pos.push({row+1,col});
//                         pos.push({row,col+1});
//                         pos.push({row-1,col});
//                         pos.push({row,col-1});
//                     }
//                 }
//             }
//         }

//         return ans;
        
//     }
// };
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