<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 dfs(map<pair<int , int> ,int>&visited , vector<vector<char>>&grid, int i , int j){
    visited[{i ,j}]=1;
    if(i+1<grid.size() && j<grid[i+1].size()){
        if(grid[i+1][j]=='1' && !visited[{i+1 , j}]){
            dfs(visited , grid , i+1 ,j);
        }
    }
    if(i-1>=0 && j<grid[i-1].size()){
        if(grid[i-1][j]=='1' && !visited[{i-1 , j}]){
            dfs(visited , grid , i-1 ,j);
        }
    }
    if(j+1<grid[i].size()){
        if(grid[i][j+1]=='1' && !visited[{i , j+1}]){
            dfs(visited , grid , i,j+1);
        }
    }
    if(j-1>=0){
        if(grid[i][j-1]=='1' && !visited[{i , j-1}]){
            dfs(visited , grid , i,j-1);
        }
    }

}
public:
    int numIslands(vector<vector<char>>& grid) {
        int cnt=0;
        map<pair<int,int> ,int>visited;
        for(int i =0 ; i<grid.size() ; i++){
            for(int j =0 ; j<grid[i].size() ; j++){
                if(grid[i][j] == '1' && !visited[{i ,j}]){
                    cnt++;
                    dfs(visited , grid , i ,j);
                }
            }
        }
        return cnt;
    }
};
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