Finding the largest difference between two doubles in java without arrays

Question

We're to find the difference between consecutive input values and return the largest change. My main issue is finding the correct operator to use (I think). Also I wanted it to work with negative values..

if(count > 0){
      change = Math.abs(temp) - Math.abs(temp2);
      UI.println(change);
      if(Math.abs(change) > Math.abs(bigChange)){
           bigChange = Math.abs(change);
      }
}

There's no need to add "Solved" to the question or title, this is not a forum. The question is automatically marked as answered and specially marked when you accept an aswer — Nevik Rehnel, Apr 09 '13 at 10:52

score 1 · Accepted Answer · answered Apr 09 '13 at 10:08

1

Your use of abs is incorrect. Consider the case where temp is -1 and temp2 is 1. The difference between these values is 2, but your routine will compute it as 0.

Try:

if(count > 0) {
  change = Math.abs(temp - temp2);
  UI.println(change);
  if( change > bigChange ) {
    bigChange = change;
  }
}

answered Apr 09 '13 at 10:08

ryanm

2,979
18
22

Thank you so much =) That did exactly what I was hoping for. – Dylan Macdonald Apr 09 '13 at 10:14

score 0 · Answer 2 · answered Apr 09 '13 at 10:11

if you want to find the change between to numbers you should use

change = Math.abs(temp- temp2);

instead of

 change = Math.abs(temp) - Math.abs(temp2);

Also you should initialize the variable

bigChange=0

Furthermore, since variables change and bigChange are always greater than zero you can avoid calling again Math.abs method.

if(change > bigChange)
      {
          bigChange = change;
      }

is also correct.

score 0 · Answer 3 · edited May 23 '17 at 10:25

0

It should be fairly simple:

int diff = temp - temp2;
max = Math.max(maxDifference, Math.abs(diff));
println(max).

Do you have any other requirement? Math.max and Math.min are quite optimized and are as fast as doing the comparison yourself. And it's a one-liner. See this answer as well for Math.max vs (a > b ? a : b)

Is Math.max(a,b) or (a>b)?a:b faster in Java?

edited May 23 '17 at 10:25

Community

1
1

answered Apr 09 '13 at 10:12

le-doude

3,345
2
25
55

Finding the largest difference between two doubles in java without arrays

3 Answers3