algorithm notes: leetcode#575 distribute candies

Problem

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].

Solution

Analysis

Use set to find unique candies. Distribute candies equally to brother and sister, which means the sister will get len(candies)//2 candies. But there are len(set(candies)) kinds of candies, the max number of kinds of candies the sister can get should be min(len(set(candies)), len(candies)//2).

Python implementation

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class :
    def distributeCandies(self, candies):
        """
        :type candies: List[int]
        :rtype: int
        """
        return min(len(set(candies)), len(candies)//2)

Java implementation

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class  {
    public int distributeCandies(int[] candies) {
        Set<Integer> candySet = new HashSet<>();
        
        for(int candy : candies){ candySet.add(candy); }
        
        return Math.min(candySet.size(), candies.length / 2);
    }
}

Time complexity

O(n). n is length of given list, as this solution iterates each element in the list.

Space complexity

O(n). Use set to store unique elements of the given list.

Link

575. Distribute Candies
(中文版) 算法笔记: 力扣#575 分糖果