> For the complete documentation index, see [llms.txt](https://mayanktyagi3111.gitbook.io/interview-prep/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mayanktyagi3111.gitbook.io/interview-prep/hashmap-and-hashset-and-sliding-window/untitled-8.md).

# 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: 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`

```java
class Solution {
    public int gcd(int x, int y) {
        if (y == 0)
            return x;
        if (y > x)
            return gcd(y, x);
        return gcd(y, x % y);
    }

    public boolean hasGroupsSizeX(int[] deck) {
        if (deck.length == 1)
            return false;
        Map<Integer, Integer> map = new HashMap<>();
        for (int x : deck)
            map.put(x, map.getOrDefault(x, 0) + 1);
        if (map.size() == 1)
            return true;
        int gcd = 1, index = 0;
        boolean first = true;
        int[] numbers = new int[map.size()];
        for (int x : map.keySet())
            numbers[index++] = x;
        for (int i = 1; i < numbers.length; i++) {
            if (first) {
                gcd = gcd(map.get(numbers[i]), map.get(numbers[i - 1]));
                first = false;
            } else
                gcd = gcd(gcd, map.get(numbers[i]));
        }
        return gcd >= 2;
    }
}
```