Today I have done leetcode's July LeetCoding Challenge with cpp.

July LeetCoding Challenge 29

Description

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
• 3 <= n <= 1000
• 1 <= rating[i] <= 105
• All the integers in rating are unique.

Solution

class Solution {
public:
  int numTeams(vector<int>& rating) {
    int answer = 0;
    for(int j = 1; j < rating.size() - 1; ++j) {
      int lessLeft = 0;
      int lessRight = 0;
      int greaterLeft = 0;
      int greaterRight = 0;
      for(int i = 0; i < j; ++i) {
        if(rating[i] < rating[j]) lessLeft += 1;
        else if(rating[i] > rating[j]) greaterLeft += 1;
      }
      for(int k = j + 1; k < rating.size(); ++k) {
        if(rating[k] < rating[j]) lessRight += 1;
        else if(rating[k] > rating[j]) greaterRight += 1;
      }
      answer += lessLeft * greaterRight + lessRight * greaterLeft;
    }
    return answer;
  }
};