算法系列（20） Leetcode 575. Distribute Candies

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:
The length of the given array is in range [2, 10,000], and will be even.
The number in given array is in range [-100,000, 100,000].
思路：主要是算出来有多少种蜡烛，用set能够很好的达到去重效果

/**
* @param {number[]} candies
* @return {number}
*/
var distributeCandies = function(candies) {
var len1 = candies.length;
var set = new Set(candies);
var len2 = set.size;
if(len2>=len1/2){
return len1/2;
}else{
return len2;
}
};