Friends Of Appropriate Ages LeetCode solution in JavaScript

1
var numFriendRequests = function (ages) {
2
  const count = new Array(121).fill(0);
3

4
  ages.forEach((age) => count[age]++);
5

6
  let res = 0; // total friend request sent
7
  let tot = 0; // cumulative count of people so far
8

9
  for (let i = 0; i <= 120; i++) {
10
    if (i > 14 && count[i] != 0) {
11
      const limit = Math.floor(0.5 * i) + 7;
12
      const rest = tot - count[limit];
13

14
      res += count[i] * rest; // current age group send friend request to other people who are within their limit
15
      res += count[i] * (count[i] - 1); // current age group send friend request to each other
16
    }
17

18
    tot += count[i];
19
    count[i] = tot;
20
  }
21

22
  return res;
23
};