1395. Count Number of Teams
https://leetcode.com/problems/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.length1 <= n <= 2001 <= rating[i] <= 10^5
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Intuition
DFS - Number of combinations
Permutations are not expected, so increment current index by 1 in each DFS call
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