914. X of a Kind in a Deck of Cards ---------E

Q:

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: deck = [1,2,3,4,4,3,2,1]
Output: true
Explanation: Possible partition [1,1],[2,2],[3,3],[4,4].

Example 2:

Input: deck = [1,1,1,2,2,2,3,3]
Output: false´
Explanation: No possible partition.

Example 3:

Input: deck = [1]
Output: false
Explanation: No possible partition.

Example 4:

Input: deck = [1,1]
Output: true
Explanation: Possible partition [1,1].

Example 5:

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

 

Constraints:

• 1 <= deck.length <= 10^4
• 0 <= deck[i] < 10^4

A:

class Solution {
public:
    bool hasGroupsSizeX(vector<int>& deck) {
        if(deck.size()==0)
            return true;
        unordered_map<int,int> M;
        for(auto v : deck){
            M[v]+=1;
        }
        vector<int> V;
        auto iter = M.begin();
        while(iter!= M.end()){
            V.push_back(iter->second);
            iter++;
        }
        int minV = *min_element(V.begin(), V.end());
        for(int X =2; X<= minV; X++){
            bool someOneCannotDevide = false;
            for(auto k : V){
                if(k%X!=0){
                    someOneCannotDevide = true;
                    break;
                }
            }
            if(!someOneCannotDevide){
                return true;
            }
        }
        return false;
    }
};

一开始没有看明白题意。  不知道 X 是个未知数。