hasGroupsSizeX.go

/* 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]

Note:

	1 <= deck.length <= 10000
	0 <= deck[i] < 10000
*/

package larray

func hasGroupsSizeX(deck []int) bool {
	if len(deck) < 2 {
		return false
	}

	xs := map[int]int{}
	for _, v := range deck {
		if _, ok := xs[v]; ok {
			xs[v]++
		} else {
			xs[v] = 1
		}
	}

	gcd := func(a, b int) int {
		for b != 0 {
			a, b = b, a%b
		}
		return a
	}

	res := xs[deck[0]]
	for _, v := range xs {
		if res = gcd(res, v); res == 1 {
			return false
		}
	}
	return true
}