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: 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: falseĀ“
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`

914. X of a Kind in a Deck of Cards
``````struct Solution;

use std::collections::HashMap;

impl Solution {
fn gcd(a: i32, b: i32) -> i32 {
if a == 0 {
b
} else {
Self::gcd(b % a, a)
}
}

fn has_groups_size_x(deck: Vec<i32>) -> bool {
let mut hm: HashMap<i32, i32> = HashMap::new();
let mut max = 0;
for x in deck {
let count = hm.entry(x).or_default();
*count += 1;
}
for &v in hm.values() {
max = Self::gcd(max, v);
}
max >= 2
}
}

#[test]
fn test() {
let deck = vec![1, 2, 3, 4, 4, 3, 2, 1];
assert_eq!(Solution::has_groups_size_x(deck), true);
let deck = vec![1, 1, 1, 2, 2, 2, 3, 3];
assert_eq!(Solution::has_groups_size_x(deck), false);
let deck = vec![1];
assert_eq!(Solution::has_groups_size_x(deck), false);
let deck = vec![1, 1];
assert_eq!(Solution::has_groups_size_x(deck), true);
let deck = vec![1, 1, 2, 2, 2, 2];
assert_eq!(Solution::has_groups_size_x(deck), true);
}
``````