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54 lines
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54 lines
2.2 KiB
HTML
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<p>You are given a <strong>0-indexed</strong> 2D integer array <code>pairs</code> where <code>pairs[i] = [start<sub>i</sub>, end<sub>i</sub>]</code>. An arrangement of <code>pairs</code> is <strong>valid</strong> if for every index <code>i</code> where <code>1 <= i < pairs.length</code>, we have <code>end<sub>i-1</sub> == start<sub>i</sub></code>.</p>
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<p>Return <em><strong>any</strong> valid arrangement of </em><code>pairs</code>.</p>
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<p><strong>Note:</strong> The inputs will be generated such that there exists a valid arrangement of <code>pairs</code>.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<pre>
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<strong>Input:</strong> pairs = [[5,1],[4,5],[11,9],[9,4]]
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<strong>Output:</strong> [[11,9],[9,4],[4,5],[5,1]]
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<strong>Explanation:
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</strong>This is a valid arrangement since end<sub>i-1</sub> always equals start<sub>i</sub>.
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end<sub>0</sub> = 9 == 9 = start<sub>1</sub>
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end<sub>1</sub> = 4 == 4 = start<sub>2</sub>
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end<sub>2</sub> = 5 == 5 = start<sub>3</sub>
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</pre>
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<p><strong>Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> pairs = [[1,3],[3,2],[2,1]]
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<strong>Output:</strong> [[1,3],[3,2],[2,1]]
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<strong>Explanation:</strong>
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This is a valid arrangement since end<sub>i-1</sub> always equals start<sub>i</sub>.
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end<sub>0</sub> = 3 == 3 = start<sub>1</sub>
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end<sub>1</sub> = 2 == 2 = start<sub>2</sub>
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The arrangements [[2,1],[1,3],[3,2]] and [[3,2],[2,1],[1,3]] are also valid.
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</pre>
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<p><strong>Example 3:</strong></p>
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<pre>
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<strong>Input:</strong> pairs = [[1,2],[1,3],[2,1]]
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<strong>Output:</strong> [[1,2],[2,1],[1,3]]
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<strong>Explanation:</strong>
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This is a valid arrangement since end<sub>i-1</sub> always equals start<sub>i</sub>.
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end<sub>0</sub> = 2 == 2 = start<sub>1</sub>
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end<sub>1</sub> = 1 == 1 = start<sub>2</sub>
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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 <= pairs.length <= 10<sup>5</sup></code></li>
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<li><code>pairs[i].length == 2</code></li>
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<li><code>0 <= start<sub>i</sub>, end<sub>i</sub> <= 10<sup>9</sup></code></li>
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<li><code>start<sub>i</sub> != end<sub>i</sub></code></li>
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<li>No two pairs are exactly the same.</li>
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<li>There <strong>exists</strong> a valid arrangement of <code>pairs</code>.</li>
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</ul>
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