575. Distribute Candies

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:

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:

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].

解题思路：

尽量将数目不同的糖果给姐姐。统计数目不同的糖果的数目n，当n大于candies.size()/2时返回candies.size()/2，否则返回candies.size()/2。

代码：

class Solution {
public:
    int distributeCandies(vector<int>& candies) {
        unordered_set<int> cand;
        for (auto tmp : candies)
            cand.insert(tmp);
        if (cand.size() > candies.size()/2) 
            return candies.size() / 2;
        else 
            return cand.size();
    }
};