leetcode 825. Friends Of Appropriate Ages

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leetcode 825. Friends Of Appropriate Ages

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原题地址：https://leetcode/problems/friends-of-appropriate-ages/

题目

Some people will make friend requests. The list of their ages is given and ages[i] is the age of the ith person.

Person A will NOT friend request person B (B != A) if any of the following conditions are true:

• age[B] <= 0.5 age[A] + 7*

• age[B] > age[A]

• age[B] > 100 && age[A] < 100

Otherwise, A will friend request B.

Note that if A requests B, B does not necessarily request A. Also, people will not friend request themselves.

How many total friend requests are made?

Example 1:
Input: [16,16]
Output: 2
Explanation: 2 people friend request each other.

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

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

Note:

• 1 <= ages.length <= 20000.
• 1 <= ages[i] <= 120.

python代码

class Solution:
    def numFriendRequests(self, ages):
        """
        :type ages: List[int]
        :rtype: int
        """
        age = collections.Counter(ages)
        res=0
        for A in age:
            for B in age:
                if A == B:
                    if B<=0.5*A+7 or B>A or (B>100 and A<100): 
                        continue
                    res += (age[A] * (age[A]-1))
                else:
                    if B<=0.5*A+7 or B>A or (B>100 and A<100): 
                        continue
                    res += age[A] * age[B]
        return res

本文标签： LeetCodeAgesFriends