Some people will make friend requests. The list of their ages is given and ages[i] is the age of the ith person.

Person A will NOT friend request person B (B != A) if any of the following conditions are true:

• age[B] < = 0.5 * age[A] + 7
• age[B] > age[A]
• age[B] > 100 & & age[A] < 100

Otherwise, A will friend request B.

Note that if A requests B, B does not necessarily request A. Also, people will not friend request themselves.

How many total friend requests are made?

Example 1:

Input: 
[16,16]

Output: 
2

Explanation: 
2 people friend request each other.

Example 2:

Input: 
[16,17,18]

Output: 
2

Explanation: 
Friend requests are made 17 -
>
 16, 18 -
>
 17.

Example 3:

Input: 
[20,30,100,110,120]

Output: 
Explanation: 
Friend requests are made 110 -
>
 100, 120 -
>
 110, 120 -
>
 100.

Notes:

• 1 < = ages.length < = 20000 .
• 1 < = ages[i] < = 120 .

class Solution {
    public int numFriendRequests(int[] ages) {

        if (ages == null || ages.length == 0) return 0;

        int[] count = new int[121];
        for (int age : ages){
            count[age]++;
        }

        int ans = 0;
        for (int i = 1; i <= 120; i++){
            for (int j = 1; j <= 120; j++){

                int countI = count[i];
                int countJ = count[j];

                if (j <= 0.5 * i + 7) continue;
                if (j > i) continue;
                if (j > 100 && i < 100) continue;

                ans += countI * countJ;

                if (i == j) ans -= countI;
            }
        }

        return ans;
    }
}