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

Rust Solution

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);
}

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