825. Friends Of Appropriate Ages
题目描述
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:
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Example 2:
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Example 3:
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题目大意
A 可以向 B请求是否可以做朋友,满足以下条件的一项,便不可做朋友:
- age[B] <= 0.5 * age[A] + 7
- age[B] > age[A]
- age[B] > 100 && age[A] < 100
Notes:
- 1 <= ages.length <= 20000.
- 1 <= ages[i] <= 120.
解题思路
记录每个年龄的人数,记为
ageCount
记录小于等于当前年龄的人数,记为sumCount
由于题目要求age[B] <= 0.5 * age[A] + 7
,所以需要减去<= 0.5 * age[A] + 7
的人数。
并且需要减去自身的个数。
代码
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