Iterating through a List of 'Sets of integers'

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heartin
Iterating through a List of 'Sets of integers'

Create a method that accept a List of 'Sets of integers' and return a list with the sums of all 'Sets of integers' in the input list.

Sample Input and Output: 

A sample input will a list with 2 sets with values (1,2,3) and (4,5). The method will have to return a list with values 6 and 9.

HINT:

Method signature will look like: 

public List<Integer> addAll(List<Set<Integer>> addList)

ALL THE BEST!!!

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sneha
Program

This program has been rewritten below twice using iterator and using for-each.

public static List<Integer> addAll(List<Set<Integer>> addList){
        List <Integer> sums=new ArrayList<Integer>();
        Set<Integer> total=new HashSet<Integer>();
        int sum=0;
        Iterator itr=addList.iterator();
        while(itr.hasNext()){
            total=(Set<Integer>) itr.next();
            Iterator setitr=total.iterator();
            while(setitr.hasNext()){
                sum=sum+(Integer)setitr.next();
            }
            sums.add(sum);
            sum=0;
        }
        return sums;
    }
 
 
TESTER METHODS
public static void main(String[] args){
        
        Set<Integer> elem=new HashSet<Integer>();
        List<Set<Integer>> addList=new ArrayList<Set<Integer>>();
        
        elem.add(1);elem.add(2);elem.add(3);
        addList.add(elem);        
        elem=new HashSet<Integer>();          
        elem.add(4);elem.add(5);        
        addList.add(elem);
        
        printTheList(addAll(addList));
        
    }
 
public static void printTheList(List<Integer> test){
        for(int i:test){
            System.out.println(i);
        }
        
    }
 

Was it useful?
heartin
Feedback
  1. Set<Integer> total=new HashSet<Integer>(); is not needed, just initialize it to null.
  2. Iterator itr=addList.iterator(); should be declared using generics as Iterator<Set<Integer>> itr=addList.iterator(); and then replace total=(Set<Integer>) itr.next(); with Iterator setitr=total.iterator(); inside while.
  3. Could you also try using a foreach loop for iterating the list as it is a better and cleaner appraoch?

NOTE: If rewriting, add a note to the original one that it has been rewritten and give the new one a title 'Modified Program after Review with Iterator' and '''Modified Program after Review with ForEach'.

Was it useful?
sneha
Modified Program after Review with Iterator

public static List<Integer> addAll(List<Set<Integer>> addList){
        List <Integer> sums=new ArrayList<Integer>();
        Set<Integer> total=null;
        int sum=0;
        Iterator<Set<Integer>> itr=addList.iterator();
        while(itr.hasNext()){
            total=itr.next();
            Iterator<Integer> setitr=total.iterator();
            while(setitr.hasNext()){
                sum=sum+setitr.next();
            }
            sums.add(sum);
            sum=0;
        }        
        return sums;
    }

Was it useful?
sneha
Modified Program after Review with ForEach

public static List<Integer> addAll(List<Set<Integer>> addList){
        List <Integer> sums=new ArrayList<Integer>();
        int sum=0;        
        for(Set<Integer> set: addList){
            for(int s:set){
                sum=sum+s;
            }
            sums.add(sum);
            sum=0;
        }
        return sums;
    }

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