Bubblesort Array Ascending [closed]

问题

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Closed 6 years ago.

I have a data file that I need to sort the information by Make&&Model of vehicle. My bubblesort doesn't work, can you help me to fix my problem, please ? Thank you very much! P.S. I can't have extra methods :( if I remove getMake() method, it works but && getModel doesn't work at all :(

    public static void sortByVehicleMakeModel(Vehicle[] vehicles) {
        for(int y = 0; y < vehicles.length; y++) {
            for (int x = 0 ; x < vehicles.length - 1 ; x++){
                if((vehicles[x].getMake().compareToIgnoreCase(vehicles[x+1].getMake()) > 0) && (vehicles[x].getModel().compareToIgnoreCase(vehicles[x+1].getModel()) > 0)) {    
                    swap(vehicles, x, x + 1);
                }           
            }
        }
        for(int x = 0; x < vehicles.length - 1; x++){
            System.out.println(vehicles[x].getMake());
        }
    }

回答1:

Follow these steps to compare two vehicles:

• compare the make of the two vehicles
• if they're not equal, return the result of the comparison
• if they are equal, compare the model and return the result

You should replace the code in your if statement with a method that compares two Vehicles using the logic described above.

Something like this:

if (compareVehicles(vehicles[x], vehicles[x + 1]) > 0) {
    swap(vehicles, x, x + 1);
}

---

To do this the correct way, you should make Vehicle implement Comparable.

That way you can put the above logic in your compareTo method.

This will allow you to simply do this:

if (vehicles[x].compareTo(vehicles[x + 1]) > 0) {
    swap(vehicles, x, x + 1);
}

Here's a simple example of how to implement Comparable:

class Vehicle implements Comparable<Vehicle> {
    private String make;
    private String model;

    public int compareTo(Vehicle other) {
        if (other == null) {
            return -1;
        }
        int compareVal = make.compareToIgnoreCase(other.make);
        if (compareVal == 0) {
            return model.compareToIgnoreCase(other.model);
        }
        else {
            return compareVal;
        }
    }

}

---

Ok... since it's been a few days, I'll just show you how to do it.

public static void sortVehicles(Vehicle[] vehicles) {
    for (int i = 0; i < vehicles.length - 1; i++) {
        Vehicle curr = vehicles[i];
        Vehicle next = vehicles[i + 1];
        String currMake = curr.getMake();
        String nextMake = next.getMake();
        int compareVal = currMake.compareToIgnoreCase(nextMake);
        // if the makes are the same, we need to compare the models
        if (compareVal == 0) {
            String currModel = curr.getModel();
            String nextModel = next.getModel();
            compareVal = currModel.compareToIgnoreCase(nextModel);
        }
        if (compareVal > 0) {
            swap(vehicles, i, i + 1);
        }
    }

    for (Vehicle v : vehicles) {
        System.out.println(v.getMake());
    }
}

回答2:

Just to improve the performance(I realize for the comparison logic, @jahroy is right). I think the code of the second loop should be as below in your case: x < vehicles.length - y -1

    for(int y = 0; y < vehicles.length; y++) {
        for (int x = 0 ; x < vehicles.length - y -1 ; x++){
            if((vehicles[x].getMake().compareToIgnoreCase(vehicles[x+1].getMake()) > 0) && (vehicles[x].getModel().compareToIgnoreCase(vehicles[x+1].getModel()) > 0)) {    
                swap(vehicles, x, x + 1);
            }           
        }
    }

回答3:

here is how i fixed it:

public static void sortByVehicleMakeModel(Vehicle[] vehicles) {


    for(int y = 0; y < vehicles.length; y++) {
        for (int x = 0 ; x < vehicles.length - 1 ; x++){
            boolean compare1 = (vehicles[x].getMake().compareToIgnoreCase(vehicles[x+1].getMake()) > 0);

        if (compare1){
            swap(vehicles, x, x + 1);

        }       

    }           
}

来源：https://stackoverflow.com/questions/13576577/bubblesort-array-ascending