Question

Giving an arraylist say [3,10,9,11,10,2,9], i need to write some code to pick out the sequence [10,9,11,10].

The way this have to be done is by creating a interval from an element and then check whether the next element(s) is in that interval.

fx.:

From the element 3 we get the interval, 3*0,80 and 3*1,20 = [2.4 – 3.6]. Now checking if the next element, 10, is in that interval – its not. Move to next element, 10.

From 10 we get the interval [8 – 12]. We see that 9, 11 and 10 is in that interval, 2 is not so stop!

What i have:

import java.util.ArrayList;
import java.util.List;


public class HelloWorld {

public static void main (String[] args){
    List<Integer> tops = new ArrayList<Integer>();
    tops.add(3);
    tops.add(10);
    tops.add(9);
    tops.add(11);
    tops.add(10);
    tops.add(2);
    tops.add(9);


    List<Integer> newtops = new ArrayList<Integer>();
    for (int i = 1; i < tops.size()-1; i++){
        double minValue = tops.get(i)*0.80;
        double maxValue = tops.get(i)*1.20;
        for (int k = i+1; k < tops.size()-1; k++){
            if (tops.get(i) > minValue && tops.get(i) < maxValue){
                newtops.add(tops.get(i));
            }
            else{
                break;
            }
        }
    }System.out.println(newtops);
}
}

Output:
[10, 10, 10, 10, 9, 9, 9, 11, 11, 10]

Expected output:
[10, 9, 11, 10]

Answer 1

I think this will work. Untested…

List<Integer> list = new ArrayList<Integer>();
list.add(3);
list.add(10);
list.add(9);
list.add(11);
list.add(10);
list.add(2);
list.add(9);

List<Integer> result = new ArrayList<Integer>();
double lowerFactor = 0.8d;
double upperFactor = 1.2d;

double lowerLimit = list.get(0) * lowerFactor;
double upperLimit = list.get(0) * upperFactor;
int index = 1;
do
{
     if (lowerLimit <= list.get(index) && list.get(index) <= upperLimit)
     {
         if (result.isEmpty())
         {
             result.add(list.get(index - 1));
         }
         result.add(list.get(index));
     } else if (result.size() > 0)
     {
         break;
     } else
     {
         lowerLimit = lowerFactor * list.get(index);
         upperLimit = upperFactor * list.get(index);
     }
     index++;
} while (index < list.size());