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// X of a Kind in a Deck of Cards
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// Leetcode problem : https://leetcode.com/problems/x-of-a-kind-in-a-deck-of-cards/
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class Solution {
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  public boolean hasGroupsSizeX(int[] deck) {
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    int[] count = new int[10000];
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    for (int i : deck) count[i]++;
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    int gcd = 0;
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    for (int i : count) if (i != 0) gcd = gcd == 0 ? i : gcd(gcd, i);
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    return gcd >= 2;
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  }
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  private int gcd(int a, int b) {
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    return b == 0 ? a : gcd(b, a % b);
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  }
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}