<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:

    bool isValid(int i , int j, int r, int c,vector<vector<char>>& grid)
    {
        return i>=0 && i<r && j>=0 && j<c;
    }

    int doBFS(vector<vector<bool>>& visited, vector<vector<char>>& grid,int i, int j)
    {
        int r = grid.size();
        int c = grid[0].size();
        vector<vector<int>> dir = {{0,1},{1,0},{0,-1},{-1,0}};

        queue<vector<int>> q;
        q.push({i,j});
        visited[i][j] = true;
        while(!q.empty())
        {
            vector<int> curr = q.front();
            q.pop();
            for(int i =0;i<4;i++)
            {
                int next_x = curr[0] + dir[i][0];
                int next_y = curr[1] + dir[i][1];
                if(isValid(next_x,next_y,r,c,grid) && !visited[next_x][next_y] &&  grid[next_x][next_y] == '1')
                {
                    //cout<<"pos_x : "<<next_x<<"pos_y: "<<next_y<<endl;
                    visited[next_x][next_y] = true;
                    q.push({next_x,next_y});
                }
            }
        }

        return 1;
    }

    
    int numIslands(vector<vector<char>>& grid) {
        int r = grid.size();
        int c = grid[0].size();
        vector<vector<bool>> visited(r,vector<bool>(c,false));

        int res =0;
        for(int i =0;i<r;i++)
        {
            for(int j =0;j<c;j++)
            {
                if(!visited[i][j] && grid[i][j] == '1')
                {
                    res += doBFS(visited,grid,i,j);
                }
            }
        }

        return res;


        
    }
};
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