In a deck of cards, each card has an integer written on it.

Return true if and only if you can choose X >= 2 such that it is possible to split the entire deck into 1 or more groups of cards, where:

Each group has exactly X cards.
All the cards in each group have the same integer.
 

Example 1:

Input: [
 
1,2,3,4,4,3,2,1]
Output: true
Explanation: Possible partition [1,1],[2,2],[3,3],[4,4]
Example 2:

Input: [1,1,1,2,2,2,3,3]
Output: false
Explanation: No possible partition.
Example 3:

Input: [1]
Output: false
Explanation: No possible partition.
Example 4:

Input: [1,1]
Output: true
Explanation: Possible partition [
 
1,1]
Example 5:

Input: [1,1,2,2,2,2]
Output: true
Explanation: Possible partition [1,1],[2,2],[2,2]

Note:

1 <= deck.length <= 10000
0 <= deck[i] < 10000

這道題仔細分析之後會得到X 一定得能被deck.length整除，也一定得被每個元素出現的次數整除，才能return true

class Solution {
    public boolean hasGroupsSizeX(int[] deck) {
        
 
if(deck == null || deck.length < 2){
            return false;
        }
        int min = Integer.MAX_VALUE;
        Map<Integer, Integer> map = new HashMap<>();
        for(int num : deck){
            map.put(num, map.getOrDefault(num,0)+1);
        }
        for(int x = 2 ; x<=deck.length; x++){
            if(deck.length % x != 0){
                continue;
            }
            int count = 0;
            for(int key : map.keySet()){
                count++;
                if(map.get(key) % x != 0){
                    break;
                }
                if(count == map.size()){
                    return true;
                }
            }
            
        }
        return false;
    }
}