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44 lines
1.3 KiB
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44 lines
1.3 KiB
HTML
<p>Given a <strong>0-indexed</strong> integer array <code>nums</code>, return <em>the number of <strong>distinct</strong> quadruplets</em> <code>(a, b, c, d)</code> <em>such that:</em></p>
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<ul>
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<li><code>nums[a] + nums[b] + nums[c] == nums[d]</code>, and</li>
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<li><code>a < b < c < d</code></li>
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</ul>
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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> nums = [1,2,3,6]
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<strong>Output:</strong> 1
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<strong>Explanation:</strong> The only quadruplet that satisfies the requirement is (0, 1, 2, 3) because 1 + 2 + 3 == 6.
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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> nums = [3,3,6,4,5]
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<strong>Output:</strong> 0
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<strong>Explanation:</strong> There are no such quadruplets in [3,3,6,4,5].
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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> nums = [1,1,1,3,5]
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<strong>Output:</strong> 4
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<strong>Explanation:</strong> The 4 quadruplets that satisfy the requirement are:
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- (0, 1, 2, 3): 1 + 1 + 1 == 3
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- (0, 1, 3, 4): 1 + 1 + 3 == 5
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- (0, 2, 3, 4): 1 + 1 + 3 == 5
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- (1, 2, 3, 4): 1 + 1 + 3 == 5
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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>4 <= nums.length <= 50</code></li>
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<li><code>1 <= nums[i] <= 100</code></li>
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</ul>
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