How to sort an array and keep track of the index in java

Question

I am trying to sort (decreasing) an array of integers but keeping track of the original index.

I mean, for example if I have this array:

b[         


        

Answer 1

The OP poster's example involved sorting an array of integer. If any of the readers have a similar situation, but with an array of non-primitive types, the following is a class that handles this for arrays of non-primitives. The class takes a somewhat different approach. It leaves the original array unmodified but instead creates an array of indexes and sorts and returns that.

public class IndirectSorter> {
    public int[] sort(T args[]) {
        Integer origindex[] = new Integer[args.length];
        int retval[] = new int[args.length];
        for (int i=0; i(args));
        for (int i=0; i> implements Comparator {
        T args[];
        public IndirectCompareClass(T args[]) { this.args = args; }
        public int compare( Integer in1, Integer in2 ) {
            return args[in1.intValue()].compareTo(args[in2.intValue()]);
        }
        public boolean equals( Integer in1, Integer in2 ) {
            return args[in1.intValue()].equals(args[in2.intValue()]);
        }
    }
}

And to call it quickly you can do something like this:

public static void main(String args[] ) {
    int indexes[] = new IndirectSorter().sort(args);
    for (int i : indexes) {
        System.out.printf("original pos: %d %s\n", i, args[i] );
    }
}

Edit: If you're willing to reimplement the Arrays.sort(int[]) method, you can avoid the creation and use of Integer objects. This can be appealing.