<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) {
        vector<vector<bool>> isVisited(grid.size(), vector<bool>(grid[0].size()));
        int count = 0;
        for(int i = 0; i < grid.size(); i ++){
            for(int j = 0; j < grid[0].size(); j ++){
                if(grid[i][j] == '1' && !isVisited[i][j]){
                    // cout << "Found new island at " << i << " " << j << endl; 
                    count ++;
                    bfs(i,j, grid, isVisited);
                }
            }
        }
        return count;
    }

    void bfs(int i, int j, vector<vector<char>>& grid, vector<vector<bool>> &isVisited){
        queue<vector<int>> q;
        q.push({i, j});
        isVisited[i][j] = true;
        while(!q.empty()){
            vector<int> index = q.front();
            i = index[0];
            j = index[1];
            q.pop();

            // cout << "visiting index " << i << " " << j << endl;
            // printGraph(isVisited);
                        
            if(i + 1 < grid.size() && grid[i+1][j] == '1' && !isVisited[i+1][j]){
                isVisited[i+1][j] = true;
                q.push({i+1, j});
            }
            if(j + 1 < grid[0].size() && grid[i][j+1] == '1' && !isVisited[i][j+1]){
                isVisited[i][j+1] = true;
                q.push({i, j+1});
            }
            if(i - 1 >= 0 && grid[i-1][j] == '1' && !isVisited[i-1][j]){
                isVisited[i-1][j] = true;
                q.push({i-1, j});
            }
            if(j - 1 >= 0 && grid[i][j-1] == '1' && !isVisited[i][j-1]){
                isVisited[i][j-1] = true;
                q.push({i, j-1});
            }
        }
    }

    void printGraph(vector<vector<bool>> &isVisited){
        cout << "isVisited:" << endl;
        for(int i = 0; i < isVisited.size(); i ++){
            for(int j = 0; j < isVisited[0].size(); j ++){
                cout << isVisited[i][j] << " ";
            }
            cout << endl;
        }
    }
};
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