CODEWITHSUNDEEP
javacollectionshashmap
Chaitanya MSV
Chaitanya MSV

Reputation: 6784

Sort java HashMap by values using O(n log n) complexity

I know this question has been asked and answered many times. But almost all of the solutions have a computational complexity of O(n^2).

I am looking for a solution with O(n log n) complexity. Can someone please suggest?

Thanks heaps, Chaitanya

Upvotes: 1

Views: 5115

Answers (1)

Louis Wasserman
Louis Wasserman

Reputation: 198023

Copy the entries to a List, sort the List by values; copy back into a LinkedHashMap. I don't think a significantly better solution is even possible.

List<Entry<K, V>> entries = new ArrayList<Entry<K, V>>(map.entrySet());
Collections.sort(entries, new Comparator<Entry<K, V>>() {
  public int compare(Entry<K, V> left, Entry<K, V> right) {
    return left.getValue().compareTo(right.getValue());
  }
}
Map<K, V> sortedMap = new LinkedHashMap<K, V>(entries.size());
for (Entry<K, V> entry : entries) {
  sortedMap.put(entry.getKey(), entry.getValue());
}

Upvotes: 6

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