Partition an array into two arrays in only one pass?

Question

I'd like to pass through an array and make two new arrays: one with the elements that meet a certain condition, and one that does not.

Is this possible in one pass, or will I necessarily have to pass twice: once to determine how big the new arrays should be, and again to fill these arrays? I can see how this would work with another programming language or with a different data structure, but with java this does not seems possible.

• Kirk Woll: Just determined not to use a more appropriate data structure like an ArrayList<T>?
• SN.: It definitely would be more appropriate, but I'm wondering if this is even possible with arrays.
• user166390: @SN. It is possible. Just not for a strict definition of "one pass". The two approaches are 1) scan, create appropriate array sizes or 2) create full-sized arrays, process, and shrink (or pass around a "used length" or have another sentinel) to fit. Neither case is ideal, although it likely Just Doesn't Matter (but I second Kirk Woll ;-). This is also precisely why I avoid Java...
• stryba: OT: @pst: you are avoiding java because you can't resize arrays?
• user166390: @stryba I avoid Java because of everything it lacks that make dealing with simple collection operations painfully verbose and procedural ;-) Arrays in Java (and even the answer below) showcase this well, I think. For instance, I would much rather do: theList.partition(x => x.length > 5) or similar. (There is a correlation between the ease-of-use-of-collections and my desire to use a particular language.)

Answer 1

You want to use Arrays? Or it may be collection? If so then:

 String[] st = new String[] {"asas", "dsdsdsd", "sfdsfdsf", "dsfsdfdsfdsfs"};
 List<String> s1 = new ArrayList<String>();
 List<String> s2 = new ArrayList<String>();
 for (String s: st) {
 if (s.length>5)
 s1.add(s)
 else
 s2.add(s);
 }