题目描述：

Given an integer array with even length, where different numbers in this array represent different kinds of candies. Each number means one candy of the corresponding kind. You need to distribute these candies equally in number to brother and sister. Return the maximum number of kinds of candies the sister could gain.

Example 1:

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Input: candies = [1,1,2,2,3,3]
Output: 3
Explanation:
There are three different kinds of candies (1, 2 and 3), and two candies for each kind.
Optimal distribution: The sister has candies [1,2,3] and the brother has candies [1,2,3], too. 
The sister has three different kinds of candies.

Example 2:

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Input: candies = [1,1,2,3]
Output: 2
Explanation: For example, the sister has candies [2,3] and the brother has candies [1,1]. 
The sister has two different kinds of candies, the brother has only one kind of candies.

Note:

  1. The length of the given array is in range [2, 10,000], and will be even.
  2. The number in given array is in range [-100,000, 100,000].

很简单的数学问题，平均分n颗糖（n为偶数）给两个人，这些糖中有不同的种类，问其中一个人最多能得到多少种糖。

很显然，如果糖的种类m大于等于n/2，那么一方最多能得到n/2种糖；如果糖的种类m小于n/2，那么一方最多能得到m种糖。

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class Solution {
public:
    int distributeCandies(vector<int>& candies) {
        int size = candies.size();
        unordered_set<int> type;
        for (auto i : candies) {
            if (!type.count(i)) type.insert(i);
        }
        
        if (type.size() > size / 2) return size / 2;
        else return type.size();
    }
};