Using Map In Your VF Pages

APEX CLASS:

 public class TestMapController{
    
     public map<string,integer> data {get;set;}
    
     public TestMapController(){
         data = new map<string,integer>();
         for(Account acc: [Select Id, Name, (Select Id, Name, Email from Contacts), Phone from Account]){
             integer count = data.get(acc.name);
             if(count != null)
                count++;
            else
                count = 1;
            data.put(acc.name, count);
        }
    }
}

VisualForce Page:

<apex:page controller="TestMapController">
 <apex:pageblock title="Map Usage On VF">
 <apex:pageBlockTable value="{!data}" var="d">
     <apex:column headerValue="Account Name">
         {!d}
     </apex:column>
     <apex:column headerValue="Duplicate Count">
         {!data[d]}
     </apex:column>
 </apex:pageBlockTable>
 </apex:pageblock>
</apex:page>