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48 lines
1.4 KiB
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48 lines
1.4 KiB
HTML
<p>Find all valid combinations of <code>k</code> numbers that sum up to <code>n</code> such that the following conditions are true:</p>
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<ul>
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<li>Only numbers <code>1</code> through <code>9</code> are used.</li>
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<li>Each number is used <strong>at most once</strong>.</li>
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</ul>
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<p>Return <em>a list of all possible valid combinations</em>. The list must not contain the same combination twice, and the combinations may be returned in any order.</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> k = 3, n = 7
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<strong>Output:</strong> [[1,2,4]]
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<strong>Explanation:</strong>
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1 + 2 + 4 = 7
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There are no other valid combinations.</pre>
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<p><strong>Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> k = 3, n = 9
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<strong>Output:</strong> [[1,2,6],[1,3,5],[2,3,4]]
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<strong>Explanation:</strong>
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1 + 2 + 6 = 9
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1 + 3 + 5 = 9
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2 + 3 + 4 = 9
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There are no other valid combinations.
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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> k = 4, n = 1
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<strong>Output:</strong> []
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<strong>Explanation:</strong> There are no valid combinations.
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Using 4 different numbers in the range [1,9], the smallest sum we can get is 1+2+3+4 = 10 and since 10 > 1, there are no valid combination.
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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>2 <= k <= 9</code></li>
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<li><code>1 <= n <= 60</code></li>
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</ul>
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