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43 lines
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43 lines
2.2 KiB
HTML
<p>There are <code>n</code> computers numbered from <code>0</code> to <code>n - 1</code> connected by ethernet cables <code>connections</code> forming a network where <code>connections[i] = [a<sub>i</sub>, b<sub>i</sub>]</code> represents a connection between computers <code>a<sub>i</sub></code> and <code>b<sub>i</sub></code>. Any computer can reach any other computer directly or indirectly through the network.</p>
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<p>You are given an initial computer network <code>connections</code>. You can extract certain cables between two directly connected computers, and place them between any pair of disconnected computers to make them directly connected.</p>
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<p>Return <em>the minimum number of times you need to do this in order to make all the computers connected</em>. If it is not possible, return <code>-1</code>.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/01/02/sample_1_1677.png" style="width: 500px; height: 148px;" />
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<pre>
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<strong>Input:</strong> n = 4, connections = [[0,1],[0,2],[1,2]]
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<strong>Output:</strong> 1
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<strong>Explanation:</strong> Remove cable between computer 1 and 2 and place between computers 1 and 3.
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</pre>
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<p><strong class="example">Example 2:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/01/02/sample_2_1677.png" style="width: 500px; height: 129px;" />
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<pre>
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<strong>Input:</strong> n = 6, connections = [[0,1],[0,2],[0,3],[1,2],[1,3]]
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<strong>Output:</strong> 2
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</pre>
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<p><strong class="example">Example 3:</strong></p>
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<pre>
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<strong>Input:</strong> n = 6, connections = [[0,1],[0,2],[0,3],[1,2]]
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<strong>Output:</strong> -1
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<strong>Explanation:</strong> There are not enough cables.
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>1 <= n <= 10<sup>5</sup></code></li>
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<li><code>1 <= connections.length <= min(n * (n - 1) / 2, 10<sup>5</sup>)</code></li>
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<li><code>connections[i].length == 2</code></li>
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<li><code>0 <= a<sub>i</sub>, b<sub>i</sub> < n</code></li>
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<li><code>a<sub>i</sub> != b<sub>i</sub></code></li>
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<li>There are no repeated connections.</li>
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<li>No two computers are connected by more than one cable.</li>
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</ul>
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