<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 {
    void bfs(vector<vector<char>>& adj, int i, int j, vector<vector<int>> &vis){
        int n = adj.size();
        int m = adj[0].size();
        queue<pair<int,int>> q;
        q.push({i,j});
        vis[i][j] = 1;
        
        while(!q.empty()){
            int row = q.front().first;
            int col = q.front().second;
            q.pop();
            
            // Explore 4 directions: up, down, left, right
            for(int delrow = -1; delrow <= 1; delrow++){
                for(int delcol = -1; delcol <= 1; delcol++){
                    // Ensure only horizontal and vertical moves
                    if(abs(delrow) + abs(delcol) == 1){
                        int nrow = row + delrow;
                        int ncol = col + delcol;
                        
                        // Check boundaries and visit status
                        if(nrow >= 0 && nrow < n && ncol >= 0 && ncol < m && !vis[nrow][ncol] && adj[nrow][ncol] == '1'){
                            q.push({nrow, ncol});
                            vis[nrow][ncol] = 1;
                        }
                    }
                }
            }
        }
    }

public:
    int numIslands(vector<vector<char>>& grid) {
        int count = 0;
        vector<vector<int>> vis(grid.size(), vector<int>(grid[0].size(), 0));
        
        for(int i = 0; i < grid.size(); i++){
            for(int j = 0; j < grid[i].size(); j++){
                if(!vis[i][j] && grid[i][j] == '1'){
                    count++;
                    bfs(grid, i, j, vis);
                }
            }
        }
        
        return count;
    }
};

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