CountChild-UsingAggregateFunction-WithoutAggregate

trigger CountContact on Contact (after insert, after update, after delete, after undelete) {
    
    set<Id> setAccountid = new set<Id>();
    list<Account> lstAc = new list<Account>();
    try{
        if(trigger.isExecuting && trigger.isAfter){
            if(trigger.isDelete){
                for(Contact ct:trigger.old){
                    setAccountid.add(ct.AccountId);
                }
            }
            else{
                for(Contact ct:trigger.new){
                    setAccountid.add(ct.AccountId);
                }
            }
            
            AggregateResult[] queryContact=[select Count(Id) cti, AccountId aci from Contact where AccountID=:setAccountid
                                            GROUP BY AccountId];
            
            
            
            if(queryContact.size()>0){
                //now use foreach loop
                for(AggregateResult ar:queryContact){
                    Id AccId=(Id)ar.get('aci');
                    Integer count = (INTEGER)ar.get('cti');
                    Account act = new Account(Id=AccId);
                    act.Count_Contact__c=count;
                    lstAc.add(act);
                }
            }
            update lstAc;
        }}catch(exception ex){
            system.debug('@@@@ getLineNumber: '+ex.getLineNumber());
            system.debug('@@@@ getMessage: '+ex.getMessage());
        }
    
}


============================================without using Aggregate=============================================================

trigger CountContact on Contact (after insert, after update, after delete, after undelete) {
    
    set<Id> storeAccID = new set<Id>();
    list<Account> lstAcct= new list<Account>();
    if(trigger.isExecuting && trigger.isAfter){
        
        if(trigger.isDelete){
            for(Contact ct:trigger.old){
                storeAccID.add(ct.AccountId);
            }
        }else{
            for(Contact ct:trigger.new){
                
                storeAccID.add(ct.AccountId);
                
            }
        }
        if(storeAccID.size()>0){
            list<Account> lstAc=[select Id,(select Id from Contacts) from Account where Id=:storeAccID];
            for(Account ac:lstAc){
                Integer ContSize= (Integer)ac.Contacts.size();
                ac.Count_Contact__c=ContSize;
                lstAcct.add(ac);
            }
        }
        update lstAcct;
    }
    
}