<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:
    void bfs(deque<pair<int, int>> &adj, vector<vector<int>> &vis, vector<vector<char>>& grid){
        int x[4] = {1, -1, 0, 0};
        int y[4] = {0, 0, 1, -1};
        int xn, yn;
        while(!adj.empty()){
            auto now = adj.front();
            adj.pop_front();
            for(auto i =0;i<4;i++){
                xn = now.first+x[i];
                yn = now.second+y[i];
                // cout<<"checking ("<<xn<< yn<<")"<<endl;
                if(xn>=0&&xn<grid.size()&&yn>=0&&yn<grid[0].size()){
                    // cout<<"checking ("<<xn<< yn<<")"<<endl;
                    if(grid[xn][yn]=='1'&&vis[xn][yn]==0){
                        
                        vis[xn][yn] = 1;
                        adj.push_back({xn, yn});
                    }
                }
            }
        }
    }
    int numIslands(vector<vector<char>>& grid) {
        int m = grid.size(), n = grid[0].size();
        deque<pair<int, int>> adj;
        vector<vector<int>> vis(m);
        for(auto i =0;i<m;i++){
            for(auto j = 0; j<n; j++){
                vis[i].push_back(0);
            }
        }
        int island = 0;
        for(auto i =0;i<m;i++){
            for(auto j = 0; j<n; j++){
                // cout<<"checking x"<<i<<"y"<<j<<endl;
                if(vis[i][j]==0&&grid[i][j]=='1'){
                    cout<<"going in"<<endl;
                    adj.push_back({i, j});
                    island++;
                    bfs(adj, vis, grid);
                }
            }
        }
        return island;
    }
};
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