Count Good Triplets in an Array
You are given two 0-indexed arrays nums1 and nums2 of length n, both of which are permutations of [0, 1, ..., n - 1].
A good triplet is a set of 3 distinct values which are present in increasing order by position both in nums1 and nums2. In other words, if we consider pos1v as the index of the value v in nums1 and pos2v as the index of the value v in nums2, then a good triplet will be a set (x, y, z) where 0 <= x, y, z <= n - 1, such that pos1x < pos1y < pos1z and pos2x < pos2y < pos2z.
Return the total number of good triplets.
Example 1
Input
nums1 = [2,0,1,3], nums2 = [0,1,2,3]Output
1Out of the triplets that appear in increasing position order in nums1, only (0, 1, 3) also appears in increasing position order in nums2.
Example 2
Input
nums1 = [4,0,1,3,2], nums2 = [4,1,0,2,3]Output
4The 4 good triplets are (4,0,3), (4,0,2), (4,1,3), and (4,1,2).
Constraints
- n == nums1.length == nums2.length
- 3 <= n <= 10^5
- 0 <= nums1[i], nums2[i] <= n - 1
- nums1 and nums2 are permutations of [0, 1, ..., n - 1].
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