🌵825. Friends Of Appropriate Ages
https://leetcode.com/problems/friends-of-appropriate-ages/
js
/**
* @param {number[]} ages
* @return {number}
*/
var numFriendRequests = function(ages) {
const numInAge = new Array(121).fill(0)
for (let age of ages) {
numInAge[age]++
}
const sumInAge = new Array(121).fill(0)
for (let i = 1; i < 121; i++) {
sumInAge[i] = numInAge[i] + sumInAge[i - 1]
}
let res = 0
for (let i = 15; i < 121; i++) {
if (numInAge[i] === 0) {
continue
}
const count = sumInAge[i] - sumInAge[(i / 2 >> 0) + 7]
res += count * numInAge[i] - numInAge[i]
}
return res
}py
class Solution:
def numFriendRequests(self, ages):
"""
:type ages: List[int]
:rtype: int
"""
num_in_age = [0] * 121
for age in ages:
num_in_age[age] += 1
sum_in_age = [0] * 121
for i in range(1, 121):
sum_in_age[i] = num_in_age[i] + sum_in_age[i - 1]
res = 0
for i in range(15, 121):
if num_in_age[i] == 0:
continue
count = sum_in_age[i] - sum_in_age[i // 2 + 7]
res += count * num_in_age[i] - num_in_age[i]
return res