[leetcode-914-X of a Kind in a Deck of Cards]

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. 1 <= deck.length <= 10000
2. 0 <= deck[i] < 10000

思路：

直接暴力，首先，x一定能整除deck的长度n。而且x也一定能整除group里每一个元素个数。

bool hasGroupsSizeX(vector<int>& deck)
{
    int n = deck.size();
    if(n <= 1)return false;
    map<int,int>mp;
    for(int i = 0; i < n; i++){mp[deck[i]]++;}
   
    for(int x = 2; x <= n; x++)
    {
        if( n % x != 0)continue;
        for(auto it = mp.begin(); ;)
        {
            if(it->second % x != 0) { break;} 
            it ++;
            if(it == mp.end()){return true;}
        }         
    }
    return false;
}