CODEWITHSUNDEEP
javasortingloopsfor-loop
dave
dave

Reputation: 67

Modify sorting methods to sort in descending order

My question is if I wanted to change my sorting methods to sort in descending order what would have to be done? (Studying for a final)

My methods are as follows 

    public void selectionsort(Comparable[] array) {
    for (int i = 0; i < array.length; i++) {
        int min = i;
        for (int j = i + 1; j < array.length; j++) {
            if (array[j].compareTo(array[i]) < 0) {
                min = j;
            }
        }
        swap(array, min, i);
    }
}

public void bubblesort(Comparable[] array) {
    for (int poss = array.length; poss > 0; poss--) {
        for (int i = 0; i < poss; i++) {
            if (array[i].compareTo(array[i + 1]) > 0) {
                swap(array, i, i + 1);
            }
        }
    }
}

public static void insertionsort(Comparable[] array) {
    for (int i = 1; i < array.length; i++) {
        Comparable temp = array[i];
        int poss = 0;
        while (poss > 0 && array[poss - 1].compareTo(temp) > 0) {
            array[poss] = array[poss - 1];
            poss--;
        }
        array[poss] = temp;
    }
}

I originally thought all that would need to be done is to change my compare to the opp of what is org was. But that does not seem to work.

Upvotes: -2

Views: 70

Answers (3)

locohamster
locohamster

Reputation: 117

Create compareToReversed method that will return -compareTo result. Have a look here for inspiration

Upvotes: 0

aa333
aa333

Reputation: 2574

Write a comparator function and use it instead of the < or > symbol. Then you can control which order it's sorted in from the comparator.

Also you can have a parameter in the comparator that decides which way it sorts, and then take that as user input. So the way it gets sorted can be controlled from the command line.

Upvotes: 1

Eran
Eran

Reputation: 394006

Change array[j].compareTo(array[i]) < 0 to array[j].compareTo(array[i]) > 0.

And similarly flip < to > (and vice versa) in all your compareTo calls to reverse the order.

Upvotes: 2

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