UniqueNumberOfOccurrences.java

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

/**
 * 1207. Unique Number of Occurrences
 * @author LBW
 */
public class UniqueNumberOfOccurrences {
    public boolean uniqueOccurrences(int[] arr) {
        Map<Integer, Integer> map = new HashMap<>();
        for (int i: arr) {
            map.put(i, map.getOrDefault(i, 0) + 1);
        }
        Set<Integer> set = new HashSet<>();
        for (Integer i: map.values()) {
            if (set.contains(i))
                return false;
            set.add(i);
        }
        return true;
    }
}