2491. Circular Sentence

题目 #

You are given a positive integer array skill of even length n where skill[i] denotes the skill of the ith player. Divide the players into n / 2 teams of size 2 such that the total skill of each team is equal.

The chemistry of a team is equal to the product of the skills of the players on that team.

Return the sum of the chemistry of all the teams, or return -1 if there is no way to divide the players into teams such that the total skill of each team is equal.   Example 1:

Input: skill = [3,2,5,1,3,4]
Output: 22
Explanation:
Divide the players into the following teams: (1, 5), (2, 4), (3, 3), where each team has a total skill of 6.
The sum of the chemistry of all the teams is: 1 * 5 + 2 * 4 + 3 * 3 = 5 + 8 + 9 = 22.

Example 2:

Input: skill = [3,4]
Output: 12
Explanation:
The two players form a team with a total skill of 7.
The chemistry of the team is 3 * 4 = 12.

Example 3:

Input: skill = [1,1,2,3]
Output: -1
Explanation:
There is no way to divide the players into teams such that the total skill of each team is equal.

Constraints:

  • $2 <= skill.length <= 10^5$
  • skill.length is even.
  • 1 <= skill[i] <= 1000

思路1 排序后遍历 #

分析 #

  • 自己的想法麻烦得很，还是北大的牛逼
  • 因为所有组相加都相等，所以最大的和最小的一起，中等和中等一起
  • 那么先排序，计算最大和最小的和，然后遍历计算result，不符合相加等于对应值就是-1

代码 # 

 1func dividePlayers(skill []int) int64 {
 2	n := len(skill)
 3	sort.Ints(skill)
 4	tmp := skill[0] + skill[n-1]
 5	var result int64 = 0
 6	for i := 0; i < n/2; i++ {
 7		if tmp != skill[i] + skill[n-i-1] {
 8			return -1
 9		}
10		result += int64(skill[i]*skill[n-i-1])
11	}
12	return result
13}