algorithm - Java - Sort one array based on values of another array?

Question

I have an array of Strings that are instances of a class from external code that I would rather not change.

I also have an array of ints that was generated by calling a function on each object. So I have

A: [string1, string2, string3]

And

B: [40, 32, 34]

How do I easily sort A such that it is sorted in by the values of B. I have boost available. I want to sort A such that it is in the order:

[string2, string3, string1]

In javascript you could do this like:

B.sort(function(a,b){return A[B.indexOf(a)] < A[B.indexOf(b)];});

Answer 1

In java 8, you can do this

with a lambda:

    String[] strings = new String[]{"string1", "string2", "string3"};
    final int[] ints = new int[]{40, 32, 34};

    final List<String> stringListCopy = Arrays.asList(strings);
    ArrayList<String> sortedList = new ArrayList(stringListCopy);
    Collections.sort(sortedList, (left, right) -> ints[stringListCopy.indexOf(left)] - ints[stringListCopy.indexOf(right)]);

Or better, with Comparator:

    String[] strings = new String[]{"string1", "string2", "string3"};
    final int[] ints = new int[]{40, 32, 34};

    final List<String> stringListCopy = Arrays.asList(strings);
    ArrayList<String> sortedList = new ArrayList(stringListCopy);
    Collections.sort(sortedList, Comparator.comparing(s -> ints[stringListCopy.indexOf(s)]));