1395. Count Number of Teams

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
• 1 <= n <= 200
• 1 <= rating[i] <= 10^5

class Solution {
    public int numTeams(int[] arr) {
        int n = arr.length;
        if(n < 3) return -1;
        int res = 0;
        
        for(int i = 0; i < n - 2; i++){
            for(int j = i + 1; j < n - 1; j++){
                for(int k = j + 1; k < n; k++){
                    if(((arr[i] < arr[j]) && (arr[j] < arr[k])) || ((arr[i] > arr[j]) && (arr[j] > arr[k]))) res++;
                }
            }
        }
        return res;
    }
}

 brutal force