Add n number of integers in array to get a target number in Java?

Question

An array is taken as input from the user. The array contains integers. Add some, all, or maybe just one is enough, to get a sum as close to 100 as possible.

• The array can contain 1-100 integers
• Each integer in the array has the value between 1-100, some could be the same. The come in random order in the array
• there is no limit how many that should be added in order to get as close to 100 as possible
• If several combinations are possible or give equal answers are equally close to 100, as 99 and 101, the highest should be chosen.

My problem is that I really don´t know how to work the loops. I have tried nestling two, but I find it tricky not to know how many integers in the array that might be needed for the calculation.

My loops so far loops each integer:

//looping over all integers in the array
for (int i = 0; i < myArray.length; i++) {
    //check already here if it is close to 100?
    //compare the integer above to the next
    for (int j = i + 1; nextWeight < myArray.length; j++) {
        //the results should be saved temporary to comparision to new sums
    }
}

I know it is not much and I know it could somehow involve dynamic programming.

Does anyone have any idea that could help me on the way?

Answer 1

By my interpretation of your question, your biggest problem lies within your algorithm. You should first decide on an algorithm, then go to the coding. If I wanted to do what you are asking I would sort the array first, either in ascending or descending order. There are many sorting algorithms. However, I think what you are looking at is a subset sum problem which could be solved by a recursive binary tree traversal algorithm. I won't give you the code, but it would do the trick if you have time to research it.