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35 lines
2.0 KiB
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<p>You are given two <strong>0-indexed</strong> arrays <code>nums1</code> and <code>nums2</code> of length <code>n</code>, both of which are <strong>permutations</strong> of <code>[0, 1, ..., n - 1]</code>.</p>
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<p>A <strong>good triplet</strong> is a set of <code>3</code> <strong>distinct</strong> values which are present in <strong>increasing order</strong> by position both in <code>nums1</code> and <code>nums2</code>. In other words, if we consider <code>pos1<sub>v</sub></code> as the index of the value <code>v</code> in <code>nums1</code> and <code>pos2<sub>v</sub></code> as the index of the value <code>v</code> in <code>nums2</code>, then a good triplet will be a set <code>(x, y, z)</code> where <code>0 <= x, y, z <= n - 1</code>, such that <code>pos1<sub>x</sub> < pos1<sub>y</sub> < pos1<sub>z</sub></code> and <code>pos2<sub>x</sub> < pos2<sub>y</sub> < pos2<sub>z</sub></code>.</p>
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<p>Return <em>the <strong>total number</strong> of good triplets</em>.</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> nums1 = [2,0,1,3], nums2 = [0,1,2,3]
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<strong>Output:</strong> 1
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<strong>Explanation:</strong>
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There are 4 triplets (x,y,z) such that pos1<sub>x</sub> < pos1<sub>y</sub> < pos1<sub>z</sub>. They are (2,0,1), (2,0,3), (2,1,3), and (0,1,3).
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Out of those triplets, only the triplet (0,1,3) satisfies pos2<sub>x</sub> < pos2<sub>y</sub> < pos2<sub>z</sub>. Hence, there is only 1 good triplet.
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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> nums1 = [4,0,1,3,2], nums2 = [4,1,0,2,3]
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<strong>Output:</strong> 4
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<strong>Explanation:</strong> The 4 good triplets are (4,0,3), (4,0,2), (4,1,3), and (4,1,2).
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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>n == nums1.length == nums2.length</code></li>
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<li><code>3 <= n <= 10<sup>5</sup></code></li>
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<li><code>0 <= nums1[i], nums2[i] <= n - 1</code></li>
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<li><code>nums1</code> and <code>nums2</code> are permutations of <code>[0, 1, ..., n - 1]</code>.</li>
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</ul>
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