By Map count all contact related to Account and,store contacts into a list.Do't use trigger

Hello Raghav,

you can try this :

public class CountContacts {

public static void getAllContact(){
Map<Id,Integer> AccountIdVsContact = new Map<Id,Integer>();
Set<Id> accid =new Set<Id>();
List<contact> cont =[select Lastname,accountId from contact Limit 100];
system.debug(‘@@@@’+cont.size());
for(contact con: cont){
accid.add(con.accountid);
}

for(Id id :accid){
AccountIdVsContact.put(id, [select Lastname,accountId from contact where accountid= :id].size());
}
system.debug(‘#####’+AccountIdVsContact.values());
}
}