[LeetCode] Distribute Candies

Posted 2020-09-27 immjc

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].

题目要求把偶数个种类不同的糖果分给哥哥和妹妹两个人，要求妹妹分得的糖果种类最多。因为有2n个糖果，所以妹妹分的的糖果种类数最多为n / 2，根据set的特性将糖果的种类m计算出来。如果m > n / 2，则取 n / 2，如果m < n / 2，则取m。

class Solution {
public:
    int distributeCandies(vector<int>& candies) {
        unordered_set<int> kind;
        for (int candy : candies)
            kind.insert(candy);
        return min(kind.size(), candies.size() / 2);
    }
};
// 309 ms

 用for循环计算糖果的种类，并根据for循环的判断条件得出妹妹分得糖果种类的最大值。

class Solution {
public:
    int distributeCandies(vector<int>& candies) {
        sort(candies.begin(), candies.end());
        int kind = 1;
        for (int i = 1; i != candies.size() && kind != candies.size() / 2; i++) 
            if (candies[i] != candies[i - 1])
                kind++;
        return kind;
    }
};
// 276 ms