<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 bfsCoordinate(vector<vector<char>>& grid, vector<vector<bool>>& visited, int row, int column) {
        queue<vector<int>> toVisit;
        toVisit.push(vector<int>{row, column});
        vector<vector<int>> directions = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
        while (!toVisit.empty()) {
            vector<int> coordinates = toVisit.front();
            toVisit.pop();
            int r = coordinates[0];
            int c = coordinates[1];
            for (auto& diff : directions) {
                int dr = diff[0];
                int dc = diff[1];
                int nextR = r + dr;
                int nextC = c + dc;

                if (nextR >= 0 && nextC >= 0 && nextR < grid.size() && nextC < grid[0].size() && !visited[nextR][nextC] && grid[nextR][nextC] == '1') {
                    visited[nextR][nextC] = true;
                    toVisit.push(vector<int>{nextR, nextC});
                }
            }
        }
    }
    int numIslands(vector<vector<char>>& grid) {
        int m = grid.size();
        int n = grid[0].size();
        vector<vector<bool>> visited = vector<vector<bool>>(m, vector<bool>(n, false));
        int islands = 0;

        for (int r = 0; r < m; r++) {
            for (int c = 0; c < n; c++) {
                if (!visited[r][c] && grid[r][c] == '1') {
                    visited[r][c] = true;
                    bfsCoordinate(grid, visited, r, c);
                    islands++;
                }
            }
        }
        return islands;
    }
};
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