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Thread: Request:Generating Subsets

  1. #1
    Junior Member
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    Question Request:Generating Subsets

    anyone can help me..import java.util.Scanner;
    import java.io.PrintStream;
    import java.util.ArrayList;

    public class Subset {


    public static void main(String[] args) {

    // Initial set: it may contains repeated elements
    int members[]={1,2,3};
    // The actual set
    ArrayList<Integer> set = new ArrayList<Integer>();

    // The repeated elements would not be inserted in the actual set.
    for (int n : members) {
    if (!set.contains(n)) {
    set.add(n);
    }
    }

    // Dump the set itself
    System.out.print("Set: ");
    dump(System.out, set);

    // extracts the subset
    ArrayList<ArrayList<Integer>> subSets = getSubsets(set);

    System.out.println("Subsets:");

    // dump the subsets one by one
    for (ArrayList<Integer> subset : subSets) {
    dump(System.out, subset);
    }

    }
    private static ArrayList<ArrayList<Integer>> getSubsets(
    ArrayList<Integer> set) {

    ArrayList<ArrayList<Integer>> subsetCollection = new ArrayList<ArrayList<Integer>>();

    if (set.size() == 0) {
    subsetCollection.add(new ArrayList<Integer>());
    } else {
    ArrayList<Integer> reducedSet = new ArrayList<Integer>();

    reducedSet.addAll(set);

    int first = reducedSet.remove(0);
    ArrayList<ArrayList<Integer>> subsets = getSubsets(reducedSet);
    subsetCollection.addAll(subsets);

    subsets = getSubsets(reducedSet);

    for (ArrayList<Integer> subset : subsets) {
    subset.add(0, first);
    }

    subsetCollection.addAll(subsets);
    }

    return subsetCollection;
    }

    // This method dumps the elements of a set in one line
    // It dumps the set into the given PrintStream object.
    private static void dump(PrintStream out, ArrayList<Integer> set) {
    out.print("{");

    boolean first = true;
    for (int n : set) {
    if (first) {
    first = false;

    } else {
    out.print(", ");

    }
    out.printf("%1$d", n);
    }

    out.println("}");
    }
    }

    Set: {1, 2, 3}
    Subsets:
    {}
    {3}
    {2}
    {2, 3}
    {1}
    {1, 3}
    {1, 2}
    {1, 2, 3}
    What i want is :
    {}
    {1}
    {2}
    {1, 2}
    {3}
    {1, 3}
    {2, 3}
    {1, 2, 3}
    also i want I will be the one to input the numbers,, like having a Scanner.. and lastly also i want to get a subset of String like {bad,good,best better}.. i really appreciate all your help its for our project in algebra but arraylist is still not thought to us in programming class.. so i cant fully understand the code above.. also i dont own the code above i just copied it from my classmate which he also copied from the net.


  2. #2
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    Default Re: Request:Generating Subsets

    Post your code here with [ code ] before and [ /code ] after (without spaces). Post the exact error message your get (if you get them). Ask a specific question.
    Improving the world one idiot at a time!

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