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40 lines
1.4 KiB
HTML
40 lines
1.4 KiB
HTML
<p>An <strong>additive number</strong> is a string whose digits can form an <strong>additive sequence</strong>.</p>
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<p>A valid <strong>additive sequence</strong> should contain <strong>at least</strong> three numbers. Except for the first two numbers, each subsequent number in the sequence must be the sum of the preceding two.</p>
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<p>Given a string containing only digits, return <code>true</code> if it is an <strong>additive number</strong> or <code>false</code> otherwise.</p>
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<p><strong>Note:</strong> Numbers in the additive sequence <strong>cannot</strong> have leading zeros, so sequence <code>1, 2, 03</code> or <code>1, 02, 3</code> is invalid.</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> "112358"
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<strong>Output:</strong> true
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<strong>Explanation:</strong>
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The digits can form an additive sequence: 1, 1, 2, 3, 5, 8.
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1 + 1 = 2, 1 + 2 = 3, 2 + 3 = 5, 3 + 5 = 8
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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> "199100199"
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<strong>Output:</strong> true
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<strong>Explanation:</strong>
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The additive sequence is: 1, 99, 100, 199.
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1 + 99 = 100, 99 + 100 = 199
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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 <= num.length <= 35</code></li>
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<li><code>num</code> consists only of digits.</li>
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</ul>
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<p> </p>
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<p><strong>Follow up:</strong> How would you handle overflow for very large input integers?</p>
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