<p>You are given an integer <code>n</code>. There is an <strong>undirected</strong> graph with <code>n</code> nodes, numbered from <code>0</code> to <code>n - 1</code>. You are given a 2D integer array <code>edges</code> where <code>edges[i] = [a<sub>i</sub>, b<sub>i</sub>]</code> denotes that there exists an <strong>undirected</strong> edge connecting nodes <code>a<sub>i</sub></code> and <code>b<sub>i</sub></code>.</p>

<p>Return <em>the <strong>number of pairs</strong> of different nodes that are <strong>unreachable</strong> from each other</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2022/05/05/tc-3.png" style="width: 267px; height: 169px;" />
<pre>
<strong>Input:</strong> n = 3, edges = [[0,1],[0,2],[1,2]]
<strong>Output:</strong> 0
<strong>Explanation:</strong> There are no pairs of nodes that are unreachable from each other. Therefore, we return 0.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2022/05/05/tc-2.png" style="width: 295px; height: 269px;" />
<pre>
<strong>Input:</strong> n = 7, edges = [[0,2],[0,5],[2,4],[1,6],[5,4]]
<strong>Output:</strong> 14
<strong>Explanation:</strong> There are 14 pairs of nodes that are unreachable from each other:
[[0,1],[0,3],[0,6],[1,2],[1,3],[1,4],[1,5],[2,3],[2,6],[3,4],[3,5],[3,6],[4,6],[5,6]].
Therefore, we return 14.
</pre>

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

<ul>
	<li><code>1 &lt;= n &lt;= 10<sup>5</sup></code></li>
	<li><code>0 &lt;= edges.length &lt;= 2 * 10<sup>5</sup></code></li>
	<li><code>edges[i].length == 2</code></li>
	<li><code>0 &lt;= a<sub>i</sub>, b<sub>i</sub> &lt; n</code></li>
	<li><code>a<sub>i</sub> != b<sub>i</sub></code></li>
	<li>There are no repeated edges.</li>
</ul>

class Solution:
    def countPairs(self, n: int, edges: List[List[int]]) -> int:
        seen = set()
        neighbor_dict = dict()

        for s, e in edges:
            if s in neighbor_dict:
                neighbor_dict[s].append(e)
            else:
                neighbor_dict[s] = [e]
            
            if e in neighbor_dict:
                neighbor_dict[e].append(s)
            else:
                neighbor_dict[e] = [s]
        
        print(neighbor_dict)


        def dfs(node, connected_list):
            if node in seen:
                return 
            seen.add(node)
            connected_list.append(node)
            if node in neighbor_dict:
                for neighbor in neighbor_dict[node]:
                    dfs(neighbor, connected_list)
        
        connected_group_list = []
        for i in range(n):
            current_connected_group = []
            dfs(i, current_connected_group)
            if len(current_connected_group) > 0:
                connected_group_list.append(current_connected_group)
        
        print(connected_group_list)
        
        connected_size_list = list(map(len, connected_group_list))

        accumulated_size_s = [connected_size_list[0]]

        for i in range(1, len(connected_size_list)):
            accumulated_size_s.append(accumulated_size_s[-1]+connected_size_list[i])
        

        result = 0

        for i in range(len(accumulated_size_s)):
            result += (accumulated_size_s[-1] - accumulated_size_s[i]) * connected_size_list[i]

        return result
            








        # seen = set()

        # def dfs(node):
        #     stack = [node]
        #     count = 0
        #     while stack:
        #         curr = stack.pop()
        #         if curr not in seen:
        #             count += 1
        #             seen.add(curr)
        #             for neighbor in graph[curr]:
        #                 if neighbor not in seen:
        #                     stack.append(neighbor)
        #     return count
        



        
1862