<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) {
        int totalIslands = 0;
        int rowSize = grid.size();
        int colSize = grid[0].size();
        
        queue<pair<int, int>> myQueue;
        for (int r = 0; r < rowSize; r++)
        {
            for (int c = 0; c < colSize; c++)
            {
                if (grid[r][c] == '1')
                {
                    totalIslands++;
                    myQueue.push(make_pair(r, c));
                    while (!myQueue.empty())
                    {
                        auto curr = myQueue.front();
                        myQueue.pop();
                        int i = curr.first;
                        int j = curr.second;
                        if (grid[i][j] == '0') continue;
                        grid[i][j] = '0';
                        
                        if (i - 1 >= 0) myQueue.push(make_pair(i - 1, j));
                        if (i + 1 < rowSize) myQueue.push(make_pair(i + 1, j));
                        if (j - 1 >= 0) myQueue.push(make_pair(i, j - 1));
                        if (j + 1 < colSize) myQueue.push(make_pair(i, j + 1));
                    }
                }
            }
        }
        
        return totalIslands;
    }
};
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