Question

I am stuck on an issue described below

Suppose we have a string like 42932-5, which has 6 numbers

I want to calculate the total sum as

4*6+2*5+9*4+3*3+2*2

How do we do this in Java?

Answer 1

I can’t say this efficent, I’m sure there’s a better way to go about it, but hay, it was fun 😛

The first thing you need to do is discard the parts of the String you don’t need

int sum = 0;
String test = "42932-5";
List<Integer> listValues = new ArrayList<Integer>(test.length());
for (int index = 0; index < test.length(); index++) {

    char value = test.charAt(index);
    if (Character.isDigit(value)) {

        listValues.add(Integer.parseInt(Character.toString(value)));

    }


}

Now, you could use a StringBuilder instead of a List, but this was what came off my head.

Next, you need to sum them

for (int index = 0; index < listValues.size(); index++) {

    sum += (listValues.get(index) * (test.length() - index - 1));

}

And I ended up with something like

(4 * 6) + (2 * 5) + (9 * 4) + (3 * 3) + (2 * 2) + (5 * 1)
= 88