<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(map<pair<int,int> , bool>& visited,int row , int col,vector<vector<char>>& grid ){
        queue<pair<int,int>> q;

        q.push({row,col});
        visited[{row,col}] = true;

        while(!q.empty()){
            pair<int,int> fnode = q.front();
            q.pop();
            int x = fnode.first;
            int y = fnode.second;

            int dx[] = {-1,0,1,0};
            int dy[] = {0,1,0,-1};
            for(int i = 0 ; i<4 ;i++){
                int newX = x + dx[i];
                int newY = y + dy[i];
                if(newX >= 0 && newX < grid.size() && newY < grid[0].size() && 
                    !visited[{newX,newY}] && grid[newX][newY] == '1'){
                        q.push({newX, newY});
                        visited[{newX,newY}] = true;
                    }
            }
        }

    }


    int numIslands(vector<vector<char>>& grid) {
        // applying bfs 
        // queue<pair<int,int>> q;
        map<pair<int,int> , bool> visited;
        int count = 0;

        // now the traversal of the matrix 
        for(int row = 0 ; row < grid.size();row++){
            int n = grid[row].size();
            for(int col = 0 ; col < n ; col++){
                if(!visited[{row,col}] && grid[row][col] == '1'){
                    bfs(visited,row,col,grid);
                    count++;
                }
            }
        }
        return count;
    
    }
};
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