<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 r=grid.size(); 
        int c=grid[0].size();
        vector<vector<int>> vis(r,vector<int>(c,0));
        int cnt=0;

        for(int i=0;i<r;i++){
            for(int j=0;j<c;j++){
                if(vis[i][j]==0 && grid[i][j]=='1') {
                    vis[i][j]=1; cnt++;
                
                    queue<vector<int>> que; que.push({i,j});
                    
                    while(!que.empty()){
                        int rcur=que.front()[0];
                        int ccur=que.front()[1]; que.pop(); 

                        for(int m=rcur-1;m<=rcur+1;m++){
                            for(int n=ccur-1;n<=ccur+1;n++){

                                if(m>=0 && n>=0 && m<r && n<c && abs(m-rcur)+abs(n-ccur)==1
                                && vis[m][n]==0 && grid[m][n]=='1'){

                                    vis[m][n]=1; 
                                    que.push({m,n});
                                }
                            }
                        }
                        
                    }
                }
            }
        }
        return cnt;
        
        
        
    }
};
27590