2491. Divide Players Into Teams of Equal Skill

Medium

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

解題

將陣列分成兩兩一組，每組加起來的值必須相同。

如果符合條件的話，從小排到大，最小+最大 = 次小 + 次大......以此類推，不符合就回傳 -1

Runtime: 82 ms, faster than 90.27%

Memory Usage: 8.4 MB, less than 80.53%

func dividePlayers(skill []int) int64 {
    // 兩個兩個一組
    sort.Ints(skill)
    ans := 0
    l := len(skill) 
    sum := skill[0] + skill[l - 1]
    
    for i:=0; i <= (l/2) - 1; i++ {
        if skill[i] + skill[l - i - 1] != sum { return int64(-1) }
        ans += skill[i] * skill[l - i - 1]
    }

    return int64(ans)
}