1395. Count number of teams

//1395. Count number of teams

class Solution {
    public int numTeams(int[] rating) {
        int n = rating.length;

        if(n < 3) {
          return 0;
        }

        int min = Integer.MAX_VALUE, max = Integer.MIN_VALUE;

        for(int num : rating) {
            min = Math.min(min, num);
            max = Math.max(max, num);
        }
        
        int[] leftTree = new int[max - min + 2];
        int[] rightTree = new int[max - min + 2];
        
        for(int num : rating) {
            update(rightTree, num - min, 1);
        }
        
        int count = 0;

        for(int i = 0; i < n; i++) {
            update(rightTree, rating[i] - min, -1);
            
            int lessLeft = query(leftTree, rating[i] - min - 1);
            int greaterLeft = i - lessLeft;
            int lessRight = query(rightTree, rating[i] - min - 1);
            int greaterRight = (n - i - 1) - lessRight;
            
            count += lessLeft * greaterRight + greaterLeft * lessRight;
            update(leftTree, rating[i] - min, 1);
        }
        
        return count;
    }

    private void update(int[] tree, int index, int value) {
        index++;

        while(index < tree.length) {
            tree[index] += value;
            index += index & (-index);
        }
    }

    private int query(int[] tree, int index) {
        int sum = 0;
        index++;

        while(index > 0) {
            sum += tree[index];
            index -= index & (-index);
        }

        return sum;
    }
}