Count friend requests based on age rules

Problem

You are given an array ages, where ages[i] is the age of the i-th person. A person of age A will send a friend request to a person of age B if all conditions hold:

1. (B > 0.5 \times A + 7)
2. (B \le A)

Each request is directed (A→B). A person cannot send a request to themselves.

Return the total number of friend requests that will be sent.

Input

• ages: integer array

Output

• An integer: total number of directed friend requests.

Constraints (you may assume typical interview bounds)

• (1 \le n \le 2\times 10^4)
• (1 \le ages[i] \le 120)

Examples

1. ages = [16, 16]

• Each 16-year-old can request the other (since (16 > 0.5\cdot16 + 7 = 15) and (16 \le 16))
• Total = 2

1. ages = [20, 30, 100, 110, 120]

• Compute total directed requests that satisfy the rules.