1395 - Count Number of Teams.

Medium

There are n soldiers standing in a line. Each soldier is assigned a unique rating value.

You have to form a team of 3 soldiers amongst them under the following rules:

• Choose 3 soldiers with index (i, j, k) with rating (rating[i], rating[j], rating[k]).

• A team is valid if: (rating[i] < rating[j] < rating[k]) or (rating[i] > rating[j] > rating[k]) where (0 <= i < j < k < n).

Return the number of teams you can form given the conditions. (soldiers can be part of multiple teams).

Example 1:

Input: rating = 2,5,3,4,1

Output: 3

Explanation: We can form three teams given the conditions. (2,3,4), (5,4,1), (5,3,1).

Example 2:

Input: rating = 2,1,3

Output: 0

Explanation: We can't form any team given the conditions.

Example 3:

Input: rating = 1,2,3,4

Output: 4

Constraints:

• n == rating.length

• 3 <= n <= 1000

• <code>1 <= ratingi<= 10⁵</code>

• All the integers in rating are unique.