Sort two arrayLists concurrently

Question

Say I have two ArrayLists:

name: [Four, Three, One, Two]
num:  [4, 3, 1, 2]

If I do: Arrays.sort(num), then I have:

name: [         


        

Answer 1

Instead of sorting the actual arrays you can have an array with just indices

a[i] = i for i = 0..n

and you can sort this array based on your numeruc array with a custom comparator. e.g.

bool compare( int a, int b ) { return num[a] < num[b]; }

Thus you have both arrays sorted by using these indices.