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Maintain another hash set with a counter as key and the value will be the key of actual hashset.

To print the values in order, just run through the hashset using counter and then get the actual value.

use LinkedHashSet

Use std::list<std::pair<X, Y> >.s that you can print the value.But problem us here you can insert duplicate value.to handle duplicate value. Use another container or map or array where u cna put value of x.and check it

Or use something like:

class HashObject {
       public Object obj;
       public long timestamp;
   }

Then have a global counter. Insert goes something like

void insert (Element e) {
       global_counter++;
       HashObject ho = new HashObject();
       ho.obj = e;
       ho.timestamp = global_counter;
       hashSet.add(ho);
   }