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class Solution {
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  public boolean uniqueOccurrences(int[] arr) {
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    Arrays.sort(arr);
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    HashSet<Integer> set = new HashSet<>();
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    int c = 1;
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    for (int i = 1; i < arr.length; i++) {
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      if (arr[i] == arr[i - 1]) c++;
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      else {
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        if (set.contains(c)) return false;
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        set.add(c);
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        c = 1;
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      }
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    }
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    if (set.contains(c)) return false;
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    return true;
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  }
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}