<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(vector<vector<char>>& grid, vector<vector<bool>>& visited, int row, int col, int n, int m) {
        visited[row][col] = true;

        queue<pair<int, int>> q;
        q.push({row, col});

        while (!q.empty()) {
            auto front = q.front();
            q.pop();

            int r = front.first;
            int c = front.second;

            vector<pair<int, int>> directions = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};

            for (auto dir : directions) {
                int newRow = r + dir.first;
                int newCol = c + dir.second;

                if (newRow >= 0 && newRow < n && newCol >= 0 && newCol < m && grid[newRow][newCol] == '1' && !visited[newRow][newCol]) 
                {
                    visited[newRow][newCol] = true;
                    q.push({newRow, newCol});
                }
            }
        }
    }

    int numIslands(vector<vector<char>>& grid) {
        int row = grid.size();
        if (row == 0) return 0;
        int col = grid[0].size();

        vector<vector<bool>> visited(row, vector<bool>(col, false));

        int count = 0;

        for (int i = 0; i < row; i++) {
            for (int j = 0; j < col; j++) {
                if (grid[i][j] == '1' && !visited[i][j]) {
                    bfs(grid, visited, i, j, row, col);
                    count++;
                }
            }
        }

        return count;
    }
}; 
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