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 pos1_v as the index of the value v in nums1 and pos2_v 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 pos1_x < pos1_y < pos1_z and pos2_x < pos2_y < pos2_z.

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 pos1_x < pos1_y < pos1_z. 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 pos2_x < pos2_y < pos2_z. 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.length
3 <= n <= 10⁵
0 <= nums1[i], nums2[i] <= n - 1
nums1 and nums2 are permutations of [0, 1, ..., n - 1].

Count Good Triplets in an Array

Problem Description

Problem Description

Answer Panel