Map of Id & List of An object for set Records of particular records.

Snippt of Code :

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Map<Id, List < Temp__c > mapAccIdListTemp = new Map<Id, List<Temp__c>>();
List<Temp__c> listTemp = new List<Temp__c>();

for(Temp__c Temp : [SELECT Id, Account__c FROM Temp__c]){            
 if(mapAccIdListTemp.containsKey(Temp.Account__c)){
  listTemp = mapAccIdListTemp.get(Temp.Account__c);
 }
 else {
  listTemp = new List<Temp__c>();
 }
 listTemp.add(Temp);
 mapAccIdListTemp.put(Temp.Account__c, listTemp);
}

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