#Leetcode# 914. X of a Kind in a Deck of Cards

https://leetcode.com/problems/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]

class Solution {
public:
    int hasGroupsSizeX(vector<int>& deck) {
        int len = deck.size();
        int num[10010];
        memset(num, 0, sizeof(num));
        if(len < 2) return false;
        for(int i = 0; i < len; i ++) num[deck[i]] ++;
        int ans = 0;
        for(int i = 0; i < 10010; i ++) {
            if(num[i]) ans = gcd(ans, num[i]);
        }
        return ans > 1;
    }
    
    int gcd(int a, int b) {
        return a == 0 ? b : gcd(b % a, a);
    }
    
};