0825. Friends Of Appropriate Ages

https://leetcode.com/problems/friends-of-appropriate-ages

Description

There are n persons on a social media website. You are given an integer array ages where ages[i] is the age of the ith person.

A Person x will not send a friend request to a person y (x != y) if any of the following conditions is true:

• age[y] <= 0.5 * age[x] + 7

• age[y] > age[x]

• age[y] > 100 && age[x] < 100

Otherwise, x will send a friend request to y.

Note that if x sends a request to y, y will not necessarily send a request to x. Also, a person will not send a friend request to themself.

Return the total number of friend requests made.

Example 1:

**Input:** ages = [16,16]
**Output:** 2
**Explanation:** 2 people friend request each other.

Example 2:

**Input:** ages = [16,17,18]
**Output:** 2
**Explanation:** Friend requests are made 17 -> 16, 18 -> 17.

Example 3:

**Input:** ages = [20,30,100,110,120]
**Output:** 3
**Explanation:** Friend requests are made 110 -> 100, 120 -> 110, 120 -> 100.

Constraints:

• n == ages.length

• 1 <= n <= 2 * 104

• 1 <= ages[i] <= 120

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