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leetcode-problemset/leetcode-cn/problem (Chinese)/统计无向图中无法互相到达点对数 [count-unreachable-pairs-of-nodes-in-an-undirected-graph].html
2022-06-29 22:54:34 +08:00

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<p>给你一个整数&nbsp;<code>n</code>&nbsp;,表示一张<strong>&nbsp;无向图</strong>&nbsp;中有 <code>n</code>&nbsp;个节点,编号为&nbsp;<code>0</code>&nbsp;&nbsp;<code>n - 1</code>&nbsp;。同时给你一个二维整数数组&nbsp;<code>edges</code>&nbsp;,其中&nbsp;<code>edges[i] = [a<sub>i</sub>, b<sub>i</sub>]</code>&nbsp;表示节点&nbsp;<code>a<sub>i</sub></code>&nbsp;<code>b<sub>i</sub></code>&nbsp;之间有一条&nbsp;<strong>无向</strong>&nbsp;边。</p>
<p>请你返回 <strong>无法互相到达</strong>&nbsp;的不同 <strong>点对数目</strong>&nbsp;</p>
<p>&nbsp;</p>
<p><strong>示例 1</strong></p>
<p><img alt="" src="https://assets.leetcode.com/uploads/2022/05/05/tc-3.png" style="width: 267px; height: 169px;"></p>
<pre><b>输入:</b>n = 3, edges = [[0,1],[0,2],[1,2]]
<b>输出:</b>0
<b>解释:</b>所有点都能互相到达,意味着没有点对无法互相到达,所以我们返回 0 。
</pre>
<p><strong>示例 2</strong></p>
<p><img alt="" src="https://assets.leetcode.com/uploads/2022/05/05/tc-2.png" style="width: 295px; height: 269px;"></p>
<pre><b>输入:</b>n = 7, edges = [[0,2],[0,5],[2,4],[1,6],[5,4]]
<b>输出:</b>14
<b>解释:</b>总共有 14 个点对互相无法到达:
[[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]]
所以我们返回 14 。
</pre>
<p>&nbsp;</p>
<p><strong>提示:</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>不会有重复边。</li>
</ul>