<p>There are <code>n</code> cities. Some of them are connected, while some are not. If city <code>a</code> is connected directly with city <code>b</code>, and city <code>b</code> is connected directly with city <code>c</code>, then city <code>a</code> is connected indirectly with city <code>c</code>.</p>

<p>A <strong>province</strong> is a group of directly or indirectly connected cities and no other cities outside of the group.</p>

<p>You are given an <code>n x n</code> matrix <code>isConnected</code> where <code>isConnected[i][j] = 1</code> if the <code>i<sup>th</sup></code> city and the <code>j<sup>th</sup></code> city are directly connected, and <code>isConnected[i][j] = 0</code> otherwise.</p>

<p>Return <em>the total number of <strong>provinces</strong></em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/12/24/graph1.jpg" style="width: 222px; height: 142px;" />
<pre>
<strong>Input:</strong> isConnected = [[1,1,0],[1,1,0],[0,0,1]]
<strong>Output:</strong> 2
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/12/24/graph2.jpg" style="width: 222px; height: 142px;" />
<pre>
<strong>Input:</strong> isConnected = [[1,0,0],[0,1,0],[0,0,1]]
<strong>Output:</strong> 3
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= n &lt;= 200</code></li>
	<li><code>n == isConnected.length</code></li>
	<li><code>n == isConnected[i].length</code></li>
	<li><code>isConnected[i][j]</code> is <code>1</code> or <code>0</code>.</li>
	<li><code>isConnected[i][i] == 1</code></li>
	<li><code>isConnected[i][j] == isConnected[j][i]</code></li>
</ul>

//#define DFS
#define BFS

class Solution {
public:
#if defined(DFS)
    int findCircleNum(std::vector<std::vector<int>> const& matrix)
    {

    }
#elif defined(BFS)
	int findCircleNum(std::vector<std::vector<int>> const& matrix)
	{
		std::unordered_map<int, std::unordered_set<int>> table{};
	
		for (auto from{0}; from < std::size(matrix); ++from)
		{
			for (auto to{0}; to < std::size(matrix[from]); ++to)
			{
				if (matrix[from][to] != 0)
				{
					table[from].insert(to);
				}
			}
		}

		auto province{0};
		std::unordered_set<int> seen{};

		for (auto from{0}; from < std::size(matrix); ++from)
		{
			if (seen.count(from) <= 0)
			{
				province = province + 1;
				std::queue<int> memory({from});
				while (!memory.empty())
				{
					auto const city{memory.front()};
					memory.pop();
					seen.insert(city);

					for (auto const to : table[city])
					{
						if (seen.count(to) <= 0)
						{
							memory.push(to);
						}
					}
				}
			}
		}
		return province;
	}
#endif
};
24000