Friends Of Appropriate Ages

arraytwo pointersbinary search

There are n persons on a social media website. You are given an integer array ages where ages[i] is the age of the i ^th 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
2 people friend request each other.

Example 2

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

Example 3

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

n == ages.length

1 <= n <= 2 * 10 ^4

1 <= ages[i] <= 120

🤔

Medium

Difficulty

Topic Info

ModuleDSA

CategoryArray

Sub-topicTwo Pointers