Question

I have this code…that does just about exactly what I need it to. It searches a predefined array of ints for two ints that sum up to a target int. However, when putting values into the vector, rather than placing them within cells, it places all the values together.
i.e. for int array[50,40,30,20,10] and target 50, rather than returning [[50][40,10][30,20]…etc.], it prints [[50,40,10,30,20…etc.]] How can I fix this?

public Vector<Vector<Integer>> subsetSum(int[] array, int target) {
    //creates vectors, adds inner vector to another vector
    outer = new Vector<Vector<Integer>>();
    inner = new Vector<Integer>();
    outer.add(inner);

    for (int k = 0; k < array.length; k++) {
        for (int l = 1; l < array.length; l++) {
            int sum = array[k]+array[l]; //sum of l and k
            if (sum == target) {
                //add l,k to vector
                inner.add(array[l]);
                inner.add(array[k]);
                //prints l and k if their sum equals target
                System.out.println(array[l]+"+"+array[k]+"="+target);
            }
            else {
                System.out.print("");
            }
        }
        //if k is the target, display
        if (array[k] == target) {
            //add k to vector
            inner.add(array[k]);
            //prints if int equals target
            System.out.println(array[k]+"="+target);
        }
    }
    //return combinations that add up to target in vector form
    return outer;
}

Answer 1

You’re only ever adding a single vector to outer. Isn’t it the case that if you find a pair that add up to the required sum, you want them in a distinct vector? So, you need to create a new “inner” vector when that happens, and add it to outer.

Remove these lines:

inner = new Vector<Integer>();
outer.add(inner);

Change:

if (sum == target) {
    inner = new Vector<Integer>();
    outer.add(inner)
    //add l,k to vector
    inner.add(array[l]);
    inner.add(array[k]);

And:

if (array[k] == target) {
    inner = new Vector<Integer>();
    outer.add(inner)
    //add k to vector
    inner.add(array[k]);

Finally, consider making inner and outer into local variables.