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40 lines
1.2 KiB
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40 lines
1.2 KiB
HTML
<p>Given a positive integer <code>n</code>, find the <strong>pivot integer</strong> <code>x</code> such that:</p>
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<ul>
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<li>The sum of all elements between <code>1</code> and <code>x</code> inclusively equals the sum of all elements between <code>x</code> and <code>n</code> inclusively.</li>
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</ul>
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<p>Return <em>the pivot integer </em><code>x</code>. If no such integer exists, return <code>-1</code>. It is guaranteed that there will be at most one pivot index for the given input.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<pre>
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<strong>Input:</strong> n = 8
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<strong>Output:</strong> 6
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<strong>Explanation:</strong> 6 is the pivot integer since: 1 + 2 + 3 + 4 + 5 + 6 = 6 + 7 + 8 = 21.
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</pre>
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<p><strong class="example">Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> n = 1
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<strong>Output:</strong> 1
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<strong>Explanation:</strong> 1 is the pivot integer since: 1 = 1.
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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 = 4
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<strong>Output:</strong> -1
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<strong>Explanation:</strong> It can be proved that no such integer exist.
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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 <= 1000</code></li>
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</ul>
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