Based on my previous learnings about auto merging duplicate accounts, I set to write code to merge contacts. 
I tested each line in developer console, it works. Of course the code is not robust and has several flaws but i will get there!  

my question is , Can someone review my code and provide constructive feedback. 
Thanks!

// Created DuplicateRule for Contacts in Setup based //on standard matching rule. 
//From the DuplicatedRecordSet, fetching all //DuplicateRecordItems, which are the duplicate //Contacts.

global class DuplicateContactMergeBatch implements Database.Batchable<sObject> {

	global Database.QueryLocator start(Database.BatchableContext bc){
       // collect the batches of records or objects to be passed to execute. 
       // DuplicateRecordSet is a list of Contacts (Duplicate RecordItems) idenified as Duplicates by the Duplicate Rule
    	
		string conduplicateruleid;
		list<DuplicateRulesId__c> cs = [select id, ContactDuplicateRuleId__c from DuplicateRulesId__c limit 1];
		if(cs!=null && cs.size() > 0 ){
			for(DuplicateRulesId__c custsetting: cs){
				
			   conduplicateruleid = custsetting.ContactDuplicateRuleId__c;
				system.debug('++++++++++++++++++    ' +conduplicateruleid);
			 }
		}

		// Fetch Id and Name of the Duplicate Record Set 

		return Database.getQueryLocator([
                SELECT id, name 
                FROM DuplicateRecordSet
                Where DuplicateRuleId = :conduplicateruleid 
            ]);  
		
    }
	
	global void execute(Database.BatchableContext BC, List<DuplicateRecordSet> scope) {
              
       //call MergeAccounts method to process each batch of records
        MergeContacts(scope); 
        
    }

	public static void  MergeContacts(List<DuplicateRecordSet> dupset){
	
		//iterate through each DuplicateRecordSet, and create a map of duplicaterecordset<Id, DuplicateRecordSet> 
		Map<Id, DuplicateRecordSet> mapDuplicateRecordSet =  new Map<Id,DuplicateRecordSet>();

		if(dupset!=null && dupset.size()>0){
			for(DuplicateRecordSet drs : dupset){
				mapDuplicateRecordSet.put(drs.Id, drs);
			}
		}
		system.debug('map of duplicate record set' +mapDuplicateRecordSet);
		Map<Id, Set<Id>> mapDuplicateRecordItem =  new Map<Id, Set<Id>>();
		for(DuplicateRecordItem drI : [SELECT Id,RecordId, DuplicateRecordSetId 
									   FROM DuplicateRecordItem 
									   where DuplicateRecordSetId IN :mapDuplicateRecordSet.keyset()]){
					
					System.debug('Duplicate record Items: ' +drI);
					if(drI!=null && !mapDuplicateRecordItem.containskey(drI.DuplicateRecordSetId)){
						mapDuplicateRecordItem.put(drI.DuplicateRecordSetId, new Set<Id>{drI.RecordId}); 
					}
					else{
						mapDuplicateRecordItem.get(drI.DuplicateRecordSetId).add(drI.RecordId); 
					}
		} 

		// create a list of contacts that need to be merged 
		list<id> lstContactId = new list<id>(); 
		Set<Id>  setContactId = new set<id>();
		list<contact> mastercontact = new list<contact>();

		// iterate through all DuplicateRecordSet records that has child records 
		for(DuplicateRecordSet dr : [SELECT Id 
									 FROM DuplicateRecordSet 
									 where Id IN : mapDuplicateRecordItem.keyset()]){
			
			// Collect all disctinct contacts from the duplicaterecorditems
			setContactId =  mapDuplicateRecordItem.get(dr.Id);
			system.debug('The elements in the setofid are :' +setContactId.size());
			system.debug('Each of these elements is :' +setContactId);                             
										 
		}

		for(Contact con : [SELECT Id, lastname,email, ownerid,phone 
							   FROM Contact 
							   WHERE Id In : setContactId 
							   order by CreatedDate DESC LIMIT 1]){		
													   
							   IF(con!=null){
								mastercontact.add(con);
							   }
							   setContactId.remove(con.Id);  
							   lstContactId.addAll(setContactId);  
		}

		system.debug('master contact ' +mastercontact[0]);
		system.debug('new elemensts in the setContactId' +setContactId);
		system.debug('list of dupicated contacts ' +lstContactId);

		if(mastercontact.size()>0 && mastercontact!=null){
			try{
				Database.merge (mastercontact[0],lstContactId, true);
			}	catch (DmlException e) {
				// Process exception
				System.debug('An unexpected error has occurred: ' + e.getMessage()); 
			} 
		}
	
	}

	global void finish(Database.BatchableContext bc){
       // execute any post-processing operations
    }   

}