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

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

• Compute total directed requests that satisfy the rules.

Friend Requests by Age

Count ordered friend requests between people using the standard age rules.

Hints

1. Start with a direct data structure representation.
2. Handle edge cases before the main loop.