Watch 10 video solutions for Count Good Triplets in an Array, a hard level problem involving Array, Binary Search, Divide and Conquer. This walkthrough by NeetCodeIO has 8,623 views views. Want to try solving it yourself? Practice on FleetCode or read the detailed text solution.
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: 1 Explanation: There are 4 triplets (x,y,z) such that pos1x < pos1y < pos1z. They are (2,0,1), (2,0,3), (2,1,3), and (0,1,3). Out of those triplets, only the triplet (0,1,3) satisfies pos2x < pos2y < pos2z. Hence, there is only 1 good triplet.
Example 2:
Input: nums1 = [4,0,1,3,2], nums2 = [4,1,0,2,3] Output: 4 Explanation: The 4 good triplets are (4,0,3), (4,0,2), (4,1,3), and (4,1,2).
Constraints:
n == nums1.length == nums2.length3 <= n <= 1050 <= nums1[i], nums2[i] <= n - 1nums1 and nums2 are permutations of [0, 1, ..., n - 1].